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FAQs about Reduction-Oxidation, ORP

Related Articles: Reduction Oxidation Potential, RedOx: A Very Valuable Tool For Assessing, Assuring Maine Aquarium Health, ppt. presentation, Part 1, Part 2, Part 3, by Bob Fenner, Re-Dox, Marine Water Quality, Maintenance, Marine Filtration, Mechanical & Chemical, Ozonizers, 

Related FAQs: Ozone 1, Ozone 2Ozone 3, & FAQs on Ozone: Rationale, System/Selection, Application/Installation, About Dryers, MeasuringMaintenance/Repair, & Marine Test Gear 1, Marine Test Gear 2, Marine Water Quality, Marine Water Quality 2, Marine Water Quality 3,

An RK2 generator and injector system.... on one of their skimmer assemblies.

Elevating ORP in RO Water -- 07/16/10
Hi all!
<<Hey there Tina!>>
I'm sure you have answered this but after searching for 2 days I can't find it.
<<Mmm, okay'¦does happen>>
What can I do to raise the ORP in my RO top-off water for my reef tank?
<<I don't know why you would need to, really (I don't recall ever hearing of anyone worrying about or 'bothering with' raising the ORP of their make-up or top-off water). But'¦there would be a few ways to do this I think. Either through increased aeration before use (also useful for blowing off excess CO2) or adding a bit of Hydrogen Peroxide to the water (do research this latter method before attempting)>>
I aerate it for 24 hrs then buffer it & aerate for another 24 hours.
<<Excellent'¦and should be sufficient here>>
I have to add about 4 quarts of water every day.
<<Okay, but really tells me nothing without the specifics of your system'¦which you have not included with this exchange>>
I am adding it slowly over the day in a small stream in an area of high flow.
<<Very good>>
When I start in the morning, the ORP is between 350 & 355. The ORP drops over the day to about 275
<<Hmm, interesting'¦and may be 'telling' about your RO water which may contain 'organics' and thus dropping the ORP. Perhaps it is time to replace the membrane'¦or maybe add a DI cartridge to the unit. But'¦ORP is a very complex dynamic that is not easily understood. A 'drop' in ORP is not necessarily an indication something 'bad' is going in to the tank. I do very much suggest you do some studying-up'¦ Here's a good place to start: http://reefkeeping.com/issues/2003-12/rhf/feature/index.php (This article has three parts'¦do read them all)>>
and after the water is all in the ORP will slowly start to come up. I have tried adding the water at night but then the next morning the ORP has only come up to about 330. Is there something I should be adding to the water besides the buffer, or is this just one of those things you have when using RO water.
<<Not so much an issue with the RO as simply a dynamic of adding 'anything' to the tank>>
My ORP will drop to about 330 during the day if I don't add any water.
<<This 'drop' in ORP is likely a result of the pH 'rising' during the daylight hours>>
I would add the water all at once but was concerned that 4 quarts of water would change the salinity too quickly for my sps corals.
<<Slow changes are generally better than quick ones. To be honest, I wouldn't worry here. ORP is always 'in flux' in our 'closed' aquatic systems. But if you want more control re'¦I suggest the addition of an ozone generator employed with a reactor (my preference to using ozone in conjunction with your skimmer)'¦when employed correctly, O3 can be very beneficial to a captive system, aside from (or as part of) elevating the ORP>>
Thanks,
Tina
<<Happy to share, Tina'¦ Eric Russell>>

Ozone and Gracilaria   8/21/08I have a 210 gallon system with a 55 gallon sump. I'm considering purchasing/using a Red Sea ozone generator, one of the ones with a ORP probe and controller all built into it, the ozone would be injected into a EV-240 protein skimmer. <Am familiar> My question being. will this end up killing my Gracilaria through lack of nutrients in the water? <Mmm... a possible effect, yes> I really like the Gracilaria as a nutrient export, plus my three tangs seem to love it. The main reason behind the ozone would be to keep my water crystal clear, provide more oxygen for the water and help keep nutrients down so I can feed heavily. However, that is the main reason behind the Gracilaria also PLUS it feeds my tangs, so if I had to pick one of the other in this instance I'd rather stick with the Gracilaria, although I do know the ozone would be more effective. <Well... I would incrementally turn up the ORP setting... see if this is having a discernible positive effect on water clarity, while not eliminating the Ogo... or grow the Red Algae elsewhere> And last question, do I have to have the skimmer effluent directly pass over carbon or can I just have carbon in my filtration? <The last> Basically, does it have to IMMEDIATELY pass over carbon or just eventually go through carbon? <Ditto> I keep a filter bag full of carbon media in my sump that I change out once a month, but I don't have any real means to pass the skimmer effluent directly onto it, it has to go through the bubble trap first and what not so that it doesn't pass tons of bubbles into the main tank. <Ah, understood> Thanks guys! <Do make it known how this turns out please. Bob Fenner>

Redox question 5/12/08 Hello <Hello.> I have a 55 g marine tank with 50 lbs live rock, Clowns, Chromis and a Batfish. <The Batfish will need a larger home.> I'm using a needle wheel, dual pump skimmer with ozone, and a 300 gph canister filter. The canister filter is new, and since a few hours after install my orp went into the upper 400's. <Way too high. 350-390 being optimal.> I'm concerned about the tank being too clean, is this something I should worry about? <Not too clean, but the danger to your fish from this ORP, if it is this high, I suspect not.> My ozone is no longer turning on, and skimmer is taking nothing out. If you can advise, thanks so much! <Three potential problems come to mind. First, if the canister's pump has a low insulation resistance it may be leaking current into the water, giving you a false reading for your ORP. Try unplugging the canister and give it a few hours to see what your ORP is then. The second possibility is your probe on the ORP meter. You will want to calibrate/replace the probe as per the manufacture's recommendations. The third possibility is that the ozone unit is stuck on, constantly running while telling you it is not. I don't think this is likely, if your ORP was really in the upper 400's you will be seeing the effects in your livestock. Also, this won't be an issue with an appropriately sized unit. Welcome, good luck, Scott V.> Re: Redox question 5/13/08 Yeah, the Batfish grew faster than I was told. <Heee, reason for a bigger tank!> The controller and probe have been cleaned and calibrated, I unplugged the ozone and canister, but the ORP hasn't dropped. <It will drop, your level will not sustain unless there is something artificially raising the ORP such as ozone or even a U.V. sterilizer (U.V. can contribute here). > Fish seem happy, corals are dying. <Not good.> Any ideas? <The old failsafe, water changes to get back to a good baseline.> When I feed it goes down but bounces back again.....thanks!! <Hmmm, something is not adding up. Everything does point to faulty readings. When you installed the canister did you rearrange other electrical equip? The proximity of can change the readings on your meter. Do use the meter to take readings in other areas/the main tank away from other electrical equipment. Possibly even shut everything else off for a moment to see if this changes your reading. Welcome, do let us know what you find, Scott V.> Re: Redox question 5/15/08 So I added a ground probe yesterday, and my orp dropped 70 points in 30 minutes, but overnight it crept back up.....I'm stumped..... <All the more to point towards some sort of electrical interference with the probe. ORP will fluctuate through the day/night anyhow. Do take measurements in other areas of the tank and shut off electrical components one by one to figure out which one is interfering. A bit of troubleshooting to do here. Good luck, Scott V.>

Ozone Concerns - 12/10/05 Hey Crew, <<Hello>> Happy holidays. <<Thanks...and to you and yours...>> I have a 180g FOWLR ~175 lbs LR with two large angels, Foxface, Heniochus, a damsel, three clowns, snails approx 30, hermits approximately 40. Water is absolutely crystal clear. <<Ok>> Tank is doing GREAT. I do use ozone <<So do I...>> injected with a dedicated pump through a Turboflotor-Multi. In order to keep the ORP at 330-340 mV I am injecting 175 mg/hr through and Aquazone ozonizer/controller. The ozonizer is on pretty much constantly. <<Ideally it would be, with the right setting on the controller...in my opinion.>> The ORP probe is in the tank and reads accurately. Water circulation is approx 10x per hour thru two wet-dries and another 1000 gal/hr circulation w/powerheads inside the tank. <<Very good>> Since I increased the circulation by adding the powerheads and cleaning my pumps to about double what it was a month ago my small Cyanobacteria problem has been cured. <<More/improved circulation is sometimes all it takes>> Is it acceptable that I use this much ozone to keep the ORP at this level? <<Sure...I have a large tank (375g) on which I run a very efficient 250 mg/hr ozone generator (Ozotech) wide open 24/7...through use of a controller of course. Since you're secure in the accuracy of the probe/controller you should be able to use as much as it takes. And since you are adding the ozone through your skimmer, any excess is being quickly blown off...though some folks feel safer by adding a small bag of carbon at the effluent output.>> Would it be better that I back off on the ozone production? <<I see no reason to here.>> I have tested the water immediately coming out of the skimmer before any carbon filtration and there is no detectable ozone even when the ozonizer is turned up this high. <<Yes...reacts/is blown off/utilized very quickly. The hobby units available really do pose little concern for residual ozone.>> I can smell the ozone under the cabinet. <<No more dangerous than an "air purifier" that uses ozone to clean the air. As long as you don't have residual ozone entering the tank (unlikely), it will be fine.>> I would like to keep the ozone going; over the past few months the most substantive changes in my system have been the addition of ozone and increased circulation. <<Both of great utility. Keep the ozone going...used responsibly as you are doing it will be of great benefit. The least of which as you have noted...water that is "absolutely crystal clear"...>> Thanks for the advice, Jimmy <<A pleasure Jimmy. Regards, EricR>>

RedOx, skimming  10/21/05 Hello Bob, I am curious as to why my ORP reading is lower (around 312) when I run my protein skimmer vs. above 400 when not using it? <Mmm, removal of charged particles, molecules, atoms by the skimmer... also increasing reaction rate... using up the 03> I stumbled upon this discovery when my skimmer pump failed and was out for a month. The ORP reading had been running 300 to 380 over the last year. Then shortly after the skimmer pump went out, ORP reading jumped to around 450. Once skimmer pump was replaced, ORP dropped back to historical levels. I am using a PINPOINT meter. I was under the assumption a protein skimmer increased the oxygen level in water column, which in turn raises the ORP reading. <Mmm, does "some things" that both raise and lower reduction/oxidation potential> I have a 90 gallon reef tank utilizing a plenum with a 5 inch sand bed. It is a lightly stocked reef with 5 fish and 60 lbs live rock. Lights on (varying intensities) for a total of 16 hours per day. Skimmer runs for 7 hours during night time. Set-up is 14 months old. Thanks for all your great insight over the years. Randy <Welcome, and I would not be (overly)concerned here. Bob Fenner> Ozone  9/10/05 I have a question about ozone generators I have one from a 500 gallon spa/hot tub it probably puts out grams instead of mg. if this is on a ORP controller does it matter? I thought I would inject it into a homemade Becket style downdraft skimmer [pvc] then into a three hundred gallon sump then back into the display. Thanks Jeff. <Jeff, shouldn't matter with that size sump imagining your display tank is over 300 gallons.  James (Salty Dog)> <<Uhh, I would use the ORP controller... set this low to start with... 150-200 mv... see how often the unit is cycling on/off... Can likely dangerously overdrive a biological system... RMF>> pH Too High? (Nope) - 08/05/05 Hello, <<Hey>> I'm terribly sorry for bothering you guys, I know you are very busy and I appreciate all your help in the past. <<No worries, happy to help.>> I have a few questions regarding pH, I was actually wondering at what level I should start to worry if it is indeed too high. <<Mmm...would strive to maintain below 8.6>> I have a 180 gallon reef with 200 lbs. of aragonite sand, about 200 lbs. of live rock.  I use a sump below the aquarium and a 42 gallon refugium next to it that is filled with various forms of macro algae, live rock and sand. <<Suggestion...keep a single species of macro algae in your 'fuge.  Algae competes for space just as corals do.  If they are fighting in your refugium they are releasing noxious chemicals to kill/retard growth of each other.  These chemicals will be/are affecting your display tank as well, not to mention keeping the algae from performing at its best as a means of nutrient export.>> On the 180 are 2x400w 20k halides and 2x110 15k VHO tubes.  On the refugium is 1x150 10k HQI and 2 65w actinics.  The sump is LifeReef design with 36" skimmer and carbon tubes.  I don't use any mechanical filtration other than the sponges in the tubes. <<Cleaned weekly I hope>> I use a Korallin calcium reactor with 10lb Co2 bottle with a fast drip and about 2 bubbles every 3 seconds (seems like a lot, but the reactor gets trapped Co2 in it, poor design I think). <<Hmm, have friends using this reactor...seem to like it fine.  I will assume you've already experimented with drip/effluent rates...measured pH of effluent.>> The system has been running for 8 months.  I've added animals slowly, I've had very few losses, algae is in check- I use a 6 stage RO and Coralife salt (and perhaps this is my problem) The source water (RO) is at pH 6.5, roughly, with an average of 5 TDS. <<Source water?  Do you mean the "effluent" from the R/O unit?.  Fairly normal readings, and a good reason to buffer all evaporation/salt makeup water.>> My ph, never falls below about 8.35 and tends to get pretty high during the extreme photo periods, I've seen 8.51 on occasion. <<Golly...these are actually quite "good" readings!  Many a marine hobbyist would love to be able constantly maintain pH values within these parameters.>> I use a controller with pH and ORP, ORP is never below 400 unless I do a big water change, at which time it dips 10-20 for a day or two, pretty normal I think. <<400 is not "normal" for most, nor necessary...would advise caution about going above this level.>> I've been toying with the photo-period on the refugium to make the pH more stable, but it still seems very high, is it dangerous at this level? <<A swing of less than .2 per day is not unstable...quite the opposite.  Your pH values are excellent in my opinion...would strive to maintain...>> My dKH is between 11 and 13, it hit 10 once when my Co2 bottle was empty and I had to wait to get it filled.  My calcium level is at 400ppm and I do not notice any animals being stressed, hard and soft corals do well, and the fish seem fine, algae is in check, present but acceptable. <<All good, but would not try to keep Alk and calcium maxed out.  The two are mutually exclusive and can cause problems at such high levels if not carefully watched (do some reading here and at the associated indexes: http://www.wetwebmedia.com/calcalkmar.htm).  I would let one or the other drop a bit.>> So, I've read, actually in a number of places, that on the reef, pH during the day can hit this level, but I was wondering if it's ok and, if it keeps rising, why and at what level I should start to worry. <<As already stated.>> Should I cut back the light on the fuge, remove a large portion of the macro algae, or leave it alone? <<Other than the "mix" of macro algae in the 'fuge and the comments on your cal/Alk, I think you're just fine.>> Honestly Baffled, Aaron <<Here's some informative reading on pH: http://www.wetwebmedia.com/calcalkmar.htm...not that baffling really <G>.  Regards, EricR>>

Reactors, Probes, pH - 08/06/05 Thanks Eric! <<Welcome Aaron>> I'll prune out everything from the fuge that is not dominant. <<Tis best my friend>> I think my ORP is set to compensate for pH, it's around 350 without the compensation. <<Mmm...the presumption would be the ORP reading is more accurate with the compensation...i.e. - 400>> I believe the Korallin reactor works well, but I can't seem to get the alkalinity or calcium level lower than this, the effluent pH is 6.5- <<Fairly common reading for reactor effluent.>> I thought perhaps I could run the RO effluent through the reactor instead of using Co2, but for the few hours I didn't use the Co2 my alkalinity started to fall, and since top off water only hits the sump a few times a day it might have an adverse effect, but it could lower my Alk enough that it's not quite so scary. <<Maybe you can try reducing the bubble count of the C02...try to increase the effluent pH to about 6.8 or so.>> I'll try to adjust the reactor again first, perhaps a new needle valve will help, mines getting a bit old. <<Most of the stock needle-valves are quite "rough", I do believe the are some aftermarket valves that are more precise...at a price of course.>> I really appreciate your help and I'll add an if/then statement to the halides that turns them off if the pH hits 8.59, trip the alarms and page me. <<Ahh...a programmer eh?  All good.>> I've never seen it get higher than 8.51, and if I don't have to worry at that level, I'll start making the other adjustments you suggested. <<Yes, not a problem.  In fact, a good level to maintain.>> On the ORP though, if I turn the pH compensation off, the reading is 350, with it on, it's 400- when you say I should be concerned about this- what do you mean exactly?  Are you saying I should be concerned about the compensated ORP or the uncompensated ORP?  And why? <<Firstly, if your probe/monitor is designed to be used with pH compensation, use this measurement.  Secondly, I didn't mean to imply an ORP reading of 400 was dangerous...it's when you get much above this (over 450) that problems can arise.  Ozone is a very powerful sanitizer (more so than chlorine), It can be very useful to aquatic systems but must be used responsibly.  For most purposes/systems an ORP reading of 350-375 is adequate...I just want to instill caution when readings start to edge above 400.>> It doesn't go any higher, and falls if I change carbon, I do 2x50 gallon water changes a month and it falls a little then, but pops back in a day or two. <<All normal...and "kudos" on the water changes.>> Also- this might be a strange one, if I measure RO (effluent) with an electric probe calibrated at 7 and 10, it reads 8.95 (unbuffered RO).  I've three different probes, and calibrated one to 4 and 7- it reads RO at 6.5- <<I believe this to be "more" accurate>> but, and perhaps this is my dilemma, if I add 2 tsp of buffer (Seachem) to about 5 gallons, the dKH hits 10, and the effluent reads 7.6. <<Yikes!  Might be a problem indeed...I believe if you read the label, one teaspoon treats 40 gallons!>> Perhaps too much raw unbuffered effluent is getting near the probe and inflating my pH values- am I off-base here or should I try to send the RO through the reactor first? <<Mmm, try easing up on the buffer first.>> It's difficult to read a reagent test for anything much above 8.3- purple is pretty much purple. <<Yes, is why I prefer an electronic pH meter.>> Why do my probes, if calibrated for sea mix measure RO effluent so high?  If I use a reagent test, it shows at 6.5.  You think RO is getting too close to the probe and inflating my PH reading?  I know it's at least 8.3 with a reg test (the tank). <<The probe calibrated with the 7 & 10 reagents performs better when reading a pH above 7.0 or so...that's why I said I believe the probe calibrated with the 4 & 7 reagents was a more accurate reading (6.5) of your RO effluent.>> Is there some way I can prevent erroneous readings using RO in an auto top off system?  I add it through my overflow into the carbon chambers, but the probe is on the other side of that, I thought the drop to the sump would ensure mixing, is it too close?  Can that cause these types of problems? <<Are you adding raw RO water to your system?  Not the best application, should be buffered (properly) before going in to your system.  As for your "problems", your calc/Alk are at their upper limits, but your pH is fine my friend.>> Thanks, Aaron <<Regards, EricR>> Silica Beads - Late Reply - 08/02/05 Hi Folks, Have a very beautiful fish only aquarium.  The air dryer for my ozonizer burst open and about 100 beads fell into my sump. I cannot get them out until tomorrow night (have to buy a water vac). I've read up and down about the silicates in your FAQ's and all points to the fact that they aren't toxic (at least for a short time) to my little friends but do I have the time to wait until tomorrow night? Best Regards, Jeffrey <<Hello Jeffrey...Sorry for the late reply.  As you've surely surmised by now, the tank will be fine till you can remove the beads.  Regards, EricR>>

Ozonizer 7/29/05 Hi!  Hope all of you are well!  I have set up an ozonizer (the one I could afford).... Red Sea brand.  Hooked it up as this:  An air pump that hooks up to a dryer.  Air in, air out.  Air out of dryer goes to ozonizer and then from ozonizer to venturi port of skimmer.  However, my skimmer is going nuts!  I am now just collecting at best, tinted water.  What to do? <Mmm, try adjusting the inflow of air, ozone... you may not actually need the air pump at all... but just a check valve twixt the skimmer and ozonizer (lest power go out, to prevent capillation...> (It is a Turboflotor).  My set-up has been explained to you all so many times that I wish I could just cut and paste some saved version of it in!  All parameters looked good.  Salt 1.025, nitrite and ammonia 0, nitrate 10ppm, KH about 12 and Ca 300ppm.  PH runs about 8.1 to 8.4.  (night/day).  Even have an oxygen test that said 7mg.  I change and clean things once a week with 20 gallons being exchanged.  I wish I could only do a 10 gallon water change, that salt gets expensive! <Try the mail-order, etailers... buy in bulk... the "two hundred gallon buckets"...> (I have a 90 gallon).  The worst part of this is that I set up the probe and did a reading right away and it was 128! <Not atypically low...> I have read it's not good if it's under 200.  Here I had beefed up circulation, built my own sump, added good algae to a chamber, etc.  and the fish can't breathe!  Or I have too many organics!  Maybe I should have left that Tidepool with BioWheel and balls, etc.  Maybe that was better!  (My nitrate was zero).  O do advise!  Thanks....... <You are learning... thank you for sharing. Bob Fenner> Ozonizers, proper levels 7/28/05 >...how many milligrams of ozone per hour ... sufficient and safe ? >This is the problem, Joe.  Bioload.   It is difficult to suggest milligrams per hour of ozone, too many variables, including bioload.  To be safe, I would get an ozone generator with controller and set the ORP level at 325.  James (Salty Dog)> Hi, James, Thanks for writing back. I appreciate that not all advisors have the same opinions, but I was sure that Bob had expressed opinions dismissing worries regarding ozone at least at certain injection rates. I was wondering if someone there could clarify that a bit, erring on the side of caution-- supposing one didn't have, wasn't going to have, an ORP controller. Although I could look into that if the necessity was felt to be universal... <Joe, is this going to be used in a pond?  Also, does the ozonizer have settings that display approximate injection levels?  James (Salty Dog)> Joe Kraska

Re: Ozonizers, proper levels 7/28/05 <<Joe, is this going to be used in a pond?>> Hrm. I found a cheap injector, not adjustable, that produces approximately 300 mg per hour. <A not-atypical sized generator for aquarium use> I'm building a pond right now (how'd ya know?), but I'll also be doing a rather large aquarium next summer. 300 gallons or so. Kind of fell into that; was doing all this research on ponds, always liked saltwater tanks (they're like art!), then became acquainted with the systemic/engineering challenges there (that, too, almost art). But my question would apply to both arenas; ponds as well as marine tanks, specifically marine reef tanks with live rock. <Could be used on either... a bit small for the/a pond use> <<Also, does the ozonizer have settings that display approximate injection levels?>> No. Joe. <Most small units do not... and not needed in almost all settings... they don't produce over-abundant O3... otherwise can be coupled with a RedOx, other monitor, controller. Bob Fenner, in HI> HLLE-And Poor Husbandry-Not Just A Coincidence... 7/22/05 I've read through the facts, and I see that HLLE (head and lateral line erosion) is caused by poor diet, poor water quality, stray voltage.. etc. <Well, it's not 100% certain what it is, but those seem to be the likely culprits!> My question is this. I recently moved from Baton Rouge to Kenner (Louisiana) and I'm sure you will agree with me when I say that usually the local fish stores and the way they do things is generally the way the hobbyists end up doing things in their own aquarium, in that city. (wow did that make sense??) <I think I'm following ya'!> What I mean is that there really is only one prominent shop in B.R., and they rely heavily on hang-on-the-back filtration, really don't utilize ozonizers, use one brand of protein skimmer etc. <I see...While mechanical filter systems have their place, I think it is a bit narrow minded to use only one methodology to the exclusion of all others....Whether it's in Baton Rouge, Boise, Honolulu, or Outer Mongolia! Hobbyists and businesses need to be open to different ideas and accept the way that there is no single best way to do things in this hobby.> And the hobbyists that shop there have tanks that reflect this method. I noticed in a lot of aquariums in Baton Rouge that HLLE was present, but obviously caused by the lack of water quality.  In these cases it was easily reversed. <Very true in most cases, as you correctly observed.> In New Orleans, there are several shops that utilize sumps, ozonizers, and calcium reactors, and the hobbyists out this way are really more in tune with their systems, and water quality. They feed really well, and frequently, and do smaller water changes. <I think that these methods are better long-term solutions for most hobbyists, despite the initial perception among many novice fish keepers and even some (retailers) that they are "more expensive", "more complicated", etc. In the long run, a better system, properly set up for a sustainable population of fishes will save countless dollars and needless fish and invert deaths. This is NOT a cheap hobby, but an initial investment will pay dividends down the line...We're on the same page here, my friend! Off the soapbox for me now!> I'm doing maintenance and have noticed, oddly enough, that even though the water quality is drastically better, and fish are getting a better diet and (theoretically) they should have no HLLE....but it is a prominent issue that I'm dealing with. I'm talking sever cases, and not just on tangs. And the only thing these customers of mine have in common is that they all have ozonizers. And the ones that don't, do not have HLLE. <Well, in the absence of other filtration adjuncts and means to improve water quality, ozone would have a much greater impact. It is an extremely valuable ally in the maintenance of healthy systems, if properly applied. Good observation by you.> I'm about to start treating with Zoe and Zoecon, (have had remarkable success with these products in the past) and my question to you is should I experiment with cutting down on the ozone? Placing it on a timer? How long should the ozone run to be effective? They are currently on 24 hours a day. <Well, I don't think that you need to run high levels of ozone, but you do want to check overall water quality parameters (such as nitrate, which is a great "yardstick" for measuring overall water quality), and it may be applicable to use a RedOx controller to monitor ORP if you are a serious user of ozone...although that might be a bit over-the-top for many hobbyists, IMO. I think that, in the end- common sense stocking and overall good husbandry-including the use of ozone, if you feel it is warranted, is the best solution. Additives such as Zoe, Selcon, etc. are always nice to enhance the nutritional value of prepared foods. Also, menu items as simple as fresh macroalgae, such as Gracilaria, do wonders for many herbivorous Tangs and Rabbitfishes (which are notoriously susceptible to HLLE). You sound like you've got a great understanding of the problems and methods to address them!> Is the HLLE and the ozone just an odd coincidence? <I don't think so. The connection between the high water quality that ozone (or other good husbandry habits) affords is no coincidence, IMO. Hobbyists who use care in stocking, maintenance and overall husbandry seem to have a much lower occurrence rate of such problems, in my experience. Keep doing what you are doing, and preach the benefits of good husbandry and observation to your friends!> Thanks (again) for your guidance, Niki -Coral Connection <It was nice to hear from you, Niki! sounds like you've got it down good! BTW, for more on the HLLE condition and some good treatment ideas, do check out a recent article by good friend and WWM/"Conscientious Aquarist" on line magazine contributor Steven Pro on this very topic in "Reefkeeping" on line magazine. A very good, nuts-and-bolts analysis of this condition. Best of luck to you! Regards, Scott F.>

HLLE...(Cont'd.) 7/27/05 Hi again Scott, <Hi there! Sorry for the delay in getting back to you!> Terribly sorry to bug you, but I don't think I quite understood the answer. Would you say that the ozone might be lending a hand in the fish becoming heavily afflicted with HLLE? <No, I don't think it is...I do think that if applied correctly, ozone can be a great assist in maintaining a cleaner environment, thus reducing the potential for diseases and maladies such as HLLE> It seems that even though I treat with food supplements, and increase water change  (smaller more frequent) that the HLLE does not go away. (As it does with tanks that have no ozone) The only correlation that I see between the tanks that have the HLLE that is not reversible is that the ozone is on 24 hours a day.  Best regards, Niki@Coral Connection <Well, Niki- I've never seen or heard of ozone as being a contributor to more serious HLLE condition. On the other hand, there is not a whole lot known about the real causes and "cures" for the condition in question. Much of what we "know" about HLLE is from anecdotal observations, etc. It's important to follow up on your theory/observation. Why not try reducing the period of time when you dose ozone, or even eliminating it entirely? Since you're basically testing a hypothesis, it's worth a try! Maybe there is a correlation in your case...Good luck! Regards, Scott F.> Ozonizers, proper levels 7/26/05 Dear Crew, I've read about ozonizers on WWM, and wish to elicit your educated opinion: Approximately how many milligrams of ozone er hour -- per gallon of water, and injected continuously -- is both sufficient to be effective, as well as safe to inject without any kind of ORP testing protocol? This probably varies slightly based on bioload, so lets be conservative. <This is the problem, Joe.  Bioload.   It is difficult to suggest milligrams per hour of ozone, too many variables, including bioload.  To be safe, I would get an ozone generator with controller and set the ORP level at 325.  James (Salty Dog)> Joe Kraska San Diego CA USA p.s. backyard renovation continues; pond digging soon... :)

Protein Skimmers And Ozone - 07/25/05 Bob, <<Eric R. here...>> What is the proper tuning of a protein skimmer that has ozone injected since the waste appears much clearer. <<"Tuning" is no different than without ozone.  You still want a thick dark skimmate, unless you're skimming "thin" for a reason (e.g.- fighting nuisance algae).  I noticed the same as you when I first added ozone...skimmate became lighter in color...and less of it.  I discovered this was due to less air being processed by the venturi on the pump to which the ozonizer was connected...in other words...the ozone didn't lessen my skimmate, the skimmer just wasn't performing as well as before.  By not using an air dryer and ensuring tubing diameter was maximized, I was able to keep the air restriction of the venturi to a minimum and restore the performance of the skimmer.  Removing/not using a dryer may not be the best option depending on the size and type (hot corona vs. cold corona, UV, etc.) ozone generator you are employing.  In this case you can try adding a tee-fitting to the pump venturi to allow more air to be drawn in.>> Regards, John

Sanders Ozonator Hook up question 7/24/05 I have a Ozone Generators by Sanders, 50-200 mg capacity I am trying to hook through the protein skimmer on my 315G aquarium but I can't seem to figure out which is the input for fresh air and which should hook to the venturi to the skimmer any input would be appreciated. <Please read here: http://www.wetwebmedia.com/redoxfaq.htm Bob Fenner>

Another Ozonizer Question - 07/23/05 My name is Bob, and this is regarding a 12 year old reef. <<Howdy Bob!>> I have done a lot of water changes over this time, and think I am burning out.... Judging from my degrading water quality. <<Um...ok(!?)>> Bob Fenner has sang the praises of Ozone for quite some time <<Many, including myself, feel he knows what he's talking about.>>, but EVERY one of my LFS are against it for the usual reasons (wipe out potential, "over clean" water. etc.. etc..)  My 3 quick questions are: <<"Over clean water?!"...excuse me while I have a chuckle...>> 1. I still plan on performing typical maint. practices, but is relying on ozone to "pick up some of the slack" improper thinking? <<Yes...ozone is an adjunct to proper maintenance/husbandry...not a replacement.>> 2. I don't plan on jacking the ORP up to the max safe limit, but to just the level needed to maintain crystal clear water (and whatever the ORP is...it is.) <<An ORP of/around 350 is a safe and useful level.>> 3. I don't read much about the long term maintenance of an Ozone system. I'm considering the Red Sea w/built in controller. <<Have read/heard good things about these...better units to be had for sure (Ozotech)...but the Red Sea units reportedly provide good service for value.>> What should I expect in terms of calibration, probe cleaning and replacement, replacement of the O/3 output device, etc.. etc.. <<Will depend on your system, amount of use, etc.... Follow the manufacturers recommendations.>> Thanks for all your help, and I suggest readers follow the link to make a donation to this wonderful site! <<Thank you for this.>> Bob <<Regards, Eric R.>>

Re- Another Ozonizer Question - 07/24/05 By " over clean" I'm referring to the elimination of micro-life, beneficial bacteria....etc.. etc.. <<Not a concern if/when applied responsibly/correctly.>> Thanks for the reply, I ordered the Red Sea...and promise not to rely on it too much! <<Excellent to hear.>> Bob

The Ozone Connection - 07/21/05 Bob, I'm sorry to bother you with a probably stupid question.   <<Only stupid when not asked...Eric R. here>> I purchased the above with a controller and hoses.  I have a built in skimmer in my filter.  How do I set this thing up? <<The ozone generator will have an output port that you will need to connect to the air input of the skimmer.  Very easy to do with venturi-type skimmers...>> I was reading on the web site that it goes into the skimmer and then filter media with Carbon under or above filter media? <<Residual ozone is of little concern in my opinion with these and most any hobby grade ozone generator when applied through a skimmer, but many still prefer to "place a small bag of carbon where the skimmer effluent will pass over/through it before reentering the tank.">> I'm new at this hobby, tanks been running since Nov.   Help!! <<Keep reading this and other such web sites, books, magazines, etc....and keep asking questions <G>...>> Thanks <<Regards, Eric R.>>

Protein Skimming, Ozone, and UV Use in Marine Filtration 7/5/05 Hello Bob, I enjoyed your article on ozonizers on www.about.com. <Actually on WWM... a link on about.com> I have a quick question for you and don't want to take too much of your time but I would appreciate your opinion. I have a 240 gallon reef with a large population of SPS and LPS corals. With the introduction of ozone to have my protein skimmer at its peak efficiency would be great. But would the introduction of ozone into the contact chamber of the skimmer kill even the beneficial microbes along with zapping bacteria, microbes and unwanted organics? <Oxidizes all indiscriminately. What most folks shoot for is "enough" O3 to reduce free-living bacteria (most ones you want are not suspended in water) and organics...> You stated in the section where you discussed the cons of using a UV Sterilizer that one of the cons of using a UV sterilizer is that you also zap beneficial microbes as well as bad. <Yes... to some extent> In a reef aquarium my corals rely on a lot of the plankton and microbes for food. Would the ozone affect this and is there any recommendations you can suggest on the usage of ozone? I look forward to your advice. Thank you, John Vu <In practical application John, folks have little lingering ozone... providing a few hundred milligrams per hour, delivered to/through your skimmer directly or not, will not harm your livestock. Bob Fenner>

Almost murdered by fish with ozone, what now? 5" Sailfin Tang and five small to medium Blue-green Chromis. New ozone generator was running fine, doing what it is supposed to do. Did a water change and turned the system back on including ozone. About 4 hours later, found tang and one Chromis is in very dire straights with the other Chromis looking tired. Hard corals were just starting to show a little stress, but nothing too bad. Shutting down ozone and adding fresh charcoal (the old stuff was only a couple days old) seemed to do the trick, so I'm sure ozone was the problem. Fish came around but tang is still a bit sluggish an hour later. Corals looked fine by then. Total time under stress was about 20 minutes. What do you think the prognosis is for a full recovery? What can I do to help recovery? <Should be fine... if not killed, burned too badly initially> ORP controller was working and only read about 240mV when fish were under stress. I checked with another meter to confirm and it was 260mV (I had just checked both with calibration solution earlier in the day so I am confident in the ORP values). ORP was 375mV before water change. <A big high... starting from?> Guess I learned the hard way that ORP is not an absolute measure of ozone hazard. I started out running Ozotech 250 into skimmer at 50%. ORP seemed to flatten so I kicked it up to 70%. After a day at 70% everything looked great. When I turned the system back on after the 20% water change, ORP was around 160mV. Since 70% seemed fine and ORP was so low, I figured that I could run it at 100% for a little while. Boy was I wrong. <... yes, once the easily oxidized material is gone from the system...> I haven't read much about people using O3 test kits with their ozone generators, usually just ORP controllers. Is it possible to use ozone generators safely with just an ORP controller (plus more patience) and no test kit? <Yes> What's a reasonable starting point for the amount of charcoal and the time between changes? <A few ounces per fifty gallons or so... switched out every few days. Bob Fenner> Regards, George Heteractis magnifica 5/24/05--Part 2 + Ozone Thanks for the info, does not seem to be growing and maybe a small amount of shrinkage so perhaps I should increase the feeding. <Sounds reasonable.> On a different topic, I emailed awhile back on ozone use and have not heard back.  <Sorry about that... with the large volume of mail that we get, we occasionally lose one!> On your site you refer to hobbyist ozone generators?? Not sure what they are, also from reading through your site it is seems to be the general opinion to run ozone 24/7. What is best way? through skimmer or ozone reactor? the unit I am getting will do 100mg and hour. Is this safe to run 24/7 with out an ORP controller?  <Ozone is used in many industries. Normal oxygen molecules are O2, ozone is O3. Forcing the extra oxygen on makes ozone a very reactive oxidizer. Small units are made specifically for aquarium use. In appropriate doses, ozone helps clarify the water by oxidizing yellowing compounds. In theory it also improves protein skimming by oxidizing organics. If overdosed, ozone can be very dangerous, oxidizing (literally burning) the tissues of living animals.  I personally would not run ozone without at least an ORP meter if not an ORP controller. If ozone is run without a controller, I would suggest running it far below the recommended level. Also, carbon must be used inline with the skimmer or ozone reactor to ensure that any free ozone gas is removed before returning to the aquarium. Ozone reactors help create large air/water interface for the ozone to dissolve and react. They probably aren't necessary if the ozone can be introduced through a skimmer.> Thanks for all the great advice and information, it has helped me through a lot of different situations. Cheers Drew <Glad to!> <<Who answered this?>>

Ozone on a Remora Pro Good Morning Crew! <Good Afternoon, Andy>       I just want to start out by saying Thanks for all the info you've given me; I've had a Marine tank for about 7 years now, and if I would have found this website things would have gone A LOT more smoothly in the beginning! I also want to take a second, and tell you even after all this time, I still learned a million things while reading The CMA, and I'm in the middle of Reef Inverts; great work, It's amazing how much information is in these books! <Thank you for your kind words.>       On to the actual question, though... I'm going to be moving my aquarium to a different room in the home (Actually, starting a new one, and tearing the old one down slowly), and after much research here, and on other sites, I've decided to try using O3 on the Aquarium with an ORP/Controller unit, still unsure on the brand, but positive it'll make a nice addition to the tank. I have e-mailed Aqua-C directly a few months ago, and was told that they don't recommend running Ozone with the Remora Pro, but stumbling through your FAQ's, I see that the crew has given people some instructions on how to do it. I've got some questions on the logistics of it, if you can help.       1. The skimmer has a Mag-3 pump, and I understand that most recommendations are to effectively "T" in an ozone line between the pump, and skimmer inlet. Are there commercially available T's, even with modification, that you know of? Or would it be better to feed the ozone at the pump Inlet? I can fab something up there...       2. The addition of "air" to the pump will produce a drop in flow; is there a way to calculate the drop, and up-size the pump accordingly? The skimmer works VERY well, I don't want to slow that down.       3. Can carbon be placed in the Pre-filter/skimmer box to filter the return water? And is it safe to have it dump into the main tank like this? I can place this in my sump if necessary, it's just a tight fit.       4. Is this thing even "Ozone Compatible", or would it just be easier to just buy a cheap, venturi skimmer not to skim, but to ozonate? If so, do you have any recommendations?       5. Or is there a better way to do this, like putting a JG fitting in the body of the skimmer?       Just some thoughts; I figured I'd ask this time, instead of doing things "My Way" and ending up with another box full of stupid equipment modifications and purchases (Anyone want a Sea-Clone 100, or a Nitrate Reductor? :)  ). Sorry for my verbose question; I've been rolling this one around in my head for a while now... :) <Andy, before I answer your questions, please reconsider using ozone.  It isn't a bad thing to do, it's just that if a tank is properly maintained, ORP levels of 300+ can be maintained without the use of it.  I only say this because of the cost of an O3 generator and controller is kind of pricey and I can think of much better things to spend money on than an ozone system.  If that is what you want to do, I'll go through this with you.  James (Salty Dog)> Thanks very much for your help- <You're welcome.> <<RMF disagrees>>             -Andy Broczkowski

ORP/Skimming Hi, I am a new aquarist and reader of your book and website, which I have found very useful and informative. Thanks for being around to answer our questions. <You're welcome> First off, my reef tank stats are the following: * 90 Gallon tank * AMiracle wet/dry trickle filter, Mag drive 90 pumping back to tank * Lighting - (4) 96W CF, 10K, and Actinic 03 Blue * AquaC - 120 protein skimmer * 120lbs live rock and 80lbs live sand (aragonite) * Some fishes, inverts, clams and coral * Tank has been operational for about 4 months with no significant problems * Water chemistry Ammonia=0, Nitrites=0, Nitrates= very low, Alkalinity=350 * SG = 1.023, started with RO/DI water and added salt mix (Instant Ocean) * Temp is a constant 80 +/-.5 degrees I have a few questions I would like to ask your opinion on. 1) The tank's ORP over night is about 250-260 (pH is 8.35), then when the lights come on it jumps to 320-330 (pH 8.00), is this normal operation? <Yes> a. Are my ORP levels too low, should I try to raise them? <ORP levels of 320/330 are very good.> b. I suspect they are low and have just purchased a Red Sea Ozonator w/controller and probe. Should I program this to try and keep the ORP in the 320-360 24x7, or will it spike even higher in the daytime? <At these levels your ORP will never exceed what the controller is set for.> c. Or should I run the unit only over night? <Personally, If I have ORP levels or 320/330, I would not have bought an ozonizer/controller.> d.   Does the ozone rich water out of the skimmer need to be charcoal filtered, or can I just run it back unto the sump? <It should be carbon filtered or you will have a rich scent of ozone in your house.  Too much may cause some nasal problems.  It is a very strong oxidizer.> 2) My protein skimmer (AquaC-120) seems to skim/foam for a while (a couple of days) then nothing for a couple of days and then back to skimming, is this normal? It doesn't seem to correlate to pH, feeding, insertion of hands into tank or addition of ESV B-Ionic Calcium Buffer. <Not unusual> Thanks for the assistance. <You're welcome.  James (Salty Dog)> Vic

ORP and skimmer questions James,  <Vic> Thanks for the reply to my questions, but it seems I have a few more. 1) I was adding the ozonizer to the system because the ORP drops over night and thought that I could/should balance the system out with ozone injection in the night time hours. a. Is this what I should do to enhance the ecosystem? Or is the ORP fluctuation from 250 to 330, perfectly fine and the usual operation of the aquarium? <<James! Answer the question/s!!! Is fine. RMF>> b. Will this additional ozone cause the ORP to raise during the day also? <<Not if all is on a controller, meter... RMF>> 2)Any suggestion on how to filter the ozone rich effluent from the skimmer? Is there a product made that will do this or is it a DIY?  <Run the skimmer water through a carbon filter. I have used one of these boxes that hang on the tank that the dealer uses to put caught fish in. Just drill a few holes in the bottom. As far as your ORP goes. ORP levels drop at night. I've read where tests in the Great Barrier Reef have given ORP levels as low as 250 in early morning. Higher ORP levels will oxidize trace elements quicker, and it is better for <limiting> algae growth. On the reefs in daylight hours, the ORP level median averages between 350 to 450. Generally though, a large drop in ORP levels at night may indicate something is not quite right in the system. A drop in ORP levels can also be caused by adding an animal, adding additives to the tank, and overfeeding. Do a Google search on "RedOx potential". I'm sure you will find plenty of reading. James (Salty Dog)>

Re: ORP and skimmer questions James, <Bob this time> Thanks again for the help. I think my confusion was based on the web  article http://www.wetwebmedia.com/redox.htm in the paragraph titled "Good" Redox Values", where it says the following: "Redox fluctuates in the wild and in captive systems throughout the day. As respiration and photosynthesis increases/decreases Redox tends to drift downward during the day, reversing the trend at night." In my experience, ORP increase during the day and decreases at night. Your article above sys just the opposite. Did I get it wrong or is there a typo? Thanks Vic <Mmm, not a typo... but a generalization that holds in ponds, fish tanks typically... Your reduction oxidation potential is higher during the day? Do you have actual data you might share? Bob Fenner>

Re: ORP and skimmer questions Bob, I sure do, data is taken once every 15 minutes with 600 points of history (approximately 6+ days worth). I will send the data once I down load it from my Neptune Systems Aqua controller III.  The data includes the following data items: Time, pH, ORP, Temp and Conductivity. I keep the info in excel with a list of all the critters in the tank. I have also notated significant events that have happened to the tank. The email trail below lists out the basics of the tank setup. More than happy to share. Thanks for your help. Vic <Mmm, have seen this reverse in trends at times, places... mainly with systems with a very great deal of photosynthetic activity. Please do send along your data for posting, discussion. Bob Fenner>

Protein Skimmer/Ozone Hi WWM crew,  <Hello Ivan> I've followed your website for quite a while and have always been very impressed. I have a question regarding ozone use. I have a 125G 2 year old reef aquarium, lightly stocked and with 140lb live rock. It has metal halide lighting, a refugium and strong circulation (6X tank vol. through sump per hour, 14X tank vol. internal circ per hour). I use a Deltec TS 1060 protein skimmer and the mix of soft and hard corals have steadily flourished over the last 18 months but I've had a battle with a persistent red slime algae over the last 3 months. I have lots of snails and hermits but they can't seem to keep up with the algae.  All water chemistry (salinity 1.024, calcium 420,pH 8.0, dKH 10,nitrite 0,nitrate 5,phosphorus 0) were ideal so I bought an ORP meter and found the ORP to be 280. I have just bought a Sander ozonizer (100mg/hour) to help this but every time I run it into my protein skimmer air inlet (as advised by Deltec), the room reeks of ozone, even with activated carbon in the skimmer chamber. I've tested all the connections and taped them up too for good measure. Can you tell me if a badly adjusted skimmer might be the problem (excessive gas venting??) also, can you give me a very rough idea how fast the ORP may increase if I can find a way to run the ozonizer continuously?? Very many thanks indeed for your help!  <Ivan, I looked on their site and could not find the model number you list, maybe an older unit. Anyway I would contact them as to the problem at http://www.deltecusa.us/  Good luck. James (Salty Dog)> 

Benefits of ozone Thanks again for some valuable information, <Welcome> After reading Bob's advice on the use of ozone I decided to buy an ozonizer and I cannot believe the difference in my tank!!!!! I had a suspected outbreak of Cryptocaryon and the ozone appears to have cleared this up and on top of this the water is now crystal clear with a significant reduction in nuisance algae. <All related benefits> Another benefit is that after adding the ozonizer I now have a newly acquired copepod population!!! thanks once again for excellent advice Frank from Glasgow <Welcome. Bob Fenner> Question about Ozone use Hi Bob, it's great to meet you, I love your book. My name's Austin, I'm a junior in high-school, I've had a 125 reef for 3 years and I'm upgrading to a 180g reef this weekend, thought I would ask your opinion on something! <Okay> I've ordered the Red-Sea 100mg ozone generator, some ozone safe tubing, an air dryer, and a controller with probe. I'm planning on injecting it into a EuroReef CS8-4 that I have. I was wondering; 1) Do I need an air pump at the air input to the ozone generator? Can it be too big, or will the ozone generator slow the air input down to what it needs? What brand/type will work best? <Likely you will not need such a pump... the intake vacuum from the skimmer will suffice> 2) As far as human safety, the skimmer collection cup has several small holes in the perimeter, would draping a bag of carbon over the collection cup keep the effluent air ozone free? <The small amount of ozone will not be detectable, dangerous... I would not be concerned here... All 03 will very likely be "consumed" in the skimmer itself> 3) As far as putting a "T" in with one end coming from ozonizer, one drawing in normal air, and one combing both and leading to the skimmer pump input,  can a regular PVC "T" from Home Depot be used? <Mmm, it can... but do look at their smaller plastic parts area... including all-plastic ball valves... you'll want one of these as well> Isn't ozone safe tubing smaller than airline tubing, how do you adapt it to fit the "T" and to fit the skimmer pump input (Sedra 5000)? <Most is adaptable to 3/16" ID use... there are other diameters available... the real up/downside of using other, less-resistant tubing is simply more frequent (like annually) replacement/renewal> What's the best way to do this (I'm all for using a different method of getting the ozone into the skimmer if there's a better way :-)? <Just having the ozone aspirated by the pump/s of the skimmer> 4) Any idea whether Euro-Reef skimmers are ozone safe? <They are "sufficiently" ozone safe> Should I get some silicon or Buna o-rings to replace the black ones? Are these found at Home Depot? <I would not be (overly) concerned here... though you are smart to ask. I would query Jeff (or his dad, Bob) Macare at EuroReef itself re these issues. Their URL somewhere here: http://www.wetwebmedia.com/euroreefskimmers.htm> 5) For effluent skimmer water, the EuroReef skimmers output is just a tube that sticks straight up, can I put a "U" onto this so the water points downward and I can have that water go into a carbon bag? Better way to do this?  <Again, I would likely dispense with this use... you can/could add the discharge "U"... but I would not> THANKS a LOT for your time!!! Austin <A pleasure to share. Bob Fenner> 

Re: Question about Ozone use (and Carbon) Thanks Crew, just one more question, I couldn't find a really good answer on WWM. Is O3 really a reactive enough molecule that the third charged O will really jump off at the first chance it gets? <Well put... ozone, tri-atomic oxygen is quite unstable... does easily "fall apart" to monatomic (very reactive oxygen) and the far more stable diatomic form> Therefore is carbon on the effluent air and water really not necessary? <Mmm, well... carbon can be of use in its absorption... but practically speaking, the puny amounts made by aquarium gear generation... are so small, usually so transient (used up) that there is very infrequently any real value in such chemical filtration> If the effluent water has to flow from one end of a 65g sump to the other with 1200gph through the sump, is it likely that the ozone will disperse before it reaches the display tank?  <Yes... not so much disperse (though this will happen) but engage in RedOx reactions> And with the airline tubing and o-rings would it work well to just replace them every year instead of trying to use different size Ozone safe tubing? Thanks a lot <Well put as well. Yes. Bob Fenner>

Ozonizer attachment Hi crew, <Frank> I have just got hold of an ozonizer that I had intended to use in conjunction with a Red Sea Prizm skimmer and its own dedicated air pump, however it appears that I cannot attach it to anything to introduce it to the water. I am thinking about using a tee piece to attach it and also let the pump in the skimmer draw air as well. Do you think this solution will work as when I attach the air pump directly to the air injector the pump stops drawing water from the tank. Is there any other solution to introduce the ozonizer to the water? <With this unit it should be able to be adjusted such that you can hook up the ozonizer discharge to the air-venturi... and adjust the valving to have this material "sucked in". Do you have a fellow marine aquarist friend there that can come over and help you in person? The folks at Red Sea should be able to describe this better. Bob Fenner> Thanks in advance for any help you can give. Frank from Glasgow 

- Ozone Generator Placement - Is it safe and effective to install an ozone generator, such as the Red Sea line with ORP monitoring, in the sump of the wet/dry filter just before the protein skimmer?<Hmm... you'd at the very least need an air pump in front of the ozone generator to force the ozone into the water. One of the most compelling reasons to use the skimmer as the mode of import is their need for air induction, which makes it a common sense location for ozone input.>  Will a significant amount of ozone escape into the ambient air?  <Provided the model you choose is not oversized, the majority of the ozone will react with compounds in the tank. Any remaining ozone that escapes into the air will likewise react very quickly. Still it's wise to implement precautions - have activated carbon in its flow path, etc. Would suggest you think about using your skimmer to process the import of ozone.>  Will that amount of ozone damage the biological filter, which is upstream but immediately adjacent?  <Shouldn't.> Richard R. <Cheers, J -- > 

- Ozone Generator Placement, Follow-up - Thanks. I'll go the way you suggest, skimmer to generator.  <Uhh... that's the other way around, ozone generator to skimmer.> Richard R. <Cheers, J -- > 

To Ozone or Not to Ozone Hey crew, thanks for all your valuable help in the past, <You're welcome>  ... it's saved me from me many times. I'm thinking of injecting ozone, currently I don't use any mechanical filtration, I use three quarts of carbon a month, LifeReef filter system with 36" skimmer, get about 1/2-1 pint of skimmate daily (stinky dead- fish dark and triggers the gag reflex if you get a whiff- should I turn it up? to get a 'wetter skimmate'?) <I wouldn't>  I use a calcium reactor with CO2 for alkalinity and calcium - effluent is 6.5, I use a Nielsen reactor for top off (mix is set at pH 11.0), this adds calcium and helps control the nighttime pH drop. I run 8.19 at the lowest, 8.32 at the highest- ORP is 375 in the morning, 364 in the evening - and this comes to my question. I know the benefits of ozone, and I know it's linked indirectly to ORP, and in many cases, ORP is the triggering factor for ozone injection - is it the only trigger I could use (even if I could monitor by slight increases in ph, I'd be happy, just don't know). Reason I'm asking is that I don't have any real need for ozone, but it greatly benefits aquaculture farms in decreasing mortality and increasing levels of DO, in the hospital, we just inject it in the vents, it's sterilizing properties are well known and I don't need to reiterate something that's been beaten to death. Real question is, how, with an ORP within acceptable limits, am I to determine if I'm adding too much?  I really didn't skimp on anything in my setup, and wouldn't skimp here, but if you say Ozone Generator to me, I'm thinking of a device that needs its own shed, has its own transformer supplying 220v AC, has a multitude of sensors and an impressive array of relays for when the unthinkable happens, not if! Sooo, on a centrally filtered marine setup with water volume somewhere in the area of 300 gallons, acceptable pH range and a respectable ORP, what are my options?  Feel free to plug a good brand if you can! Also, feel free to tell me I'm way out of control, my wife does. If I don't need it, I won't get it!  I figured I'd drop this by as well, I entertained the idea, albeit briefly, of creating an oxygen reactor, but when I brought the O2 bottle home, the wife says she won't allow it in the house, and particularly not under a fish tank with enough electricity running through it to power a small town - she says the concussive blast of a marine fish tank would be fascinating, but O2 is not something even remotely possible without alimony, sooo, ozone right?  Can I get a slight increase in pH with enough ozone? What triggers can I use? What's a good brand, and How much max should I inject?  I take it I really won't be able to get a decent amount in based on ORP will I, an interesting caveat but one I'm sure you've come across before, please help. Any help is, as always, greatly appreciated.  <Aaron, people buy ozone generators to achieve the ORP levels you are already maintaining. Those levels indicate very good maintenance/cleaning etc. Put your wallet away and make the wife happy. James (Salty Dog)> 

Ozone Use/Chlorine Detox Hello - Is it possible to use ozone in my SW mixing barrel to destroy or otherwise neutralize any present chlorine or chloramines? I'm thinking that ozone probably won't destroy chlorine, as the two are used together in spas, but it might break apart chloramine and neutralize (oxidize) the resulting '-amine' part. I should know this simple chemistry by now, sorry for the 'durr' question ... but I cannot find an answer anywhere on WWM.  <Ozone works best in oxidizing organics. Why would you want to go through the expense of using ozone anyway, when just using a product such as SeaChem's Prime will do the trick. Here is a link to water conditioning on the WWW. http://www.google.com/custom?q=Conditioners&sitesearch=wetwebmedia.com  James (Salty Dog)>

Ozone Use/Chlorine Detox Thanks James. <You're welcome>  I'm still curious what ozone does to chlorine and chloramines, if it is able to break up and / or neutralize both, or just the former or the latter. <I would do a Google search on ozone if you haven't already. May be interesting>  As a matter of fact, I do use Prime, but I happen to have an extra ozone generator. An argument could be made that over the course of 10 years, assuming the ozone maker lasts that long... <Very unlikely. The biggest enemy of the discharge units is dampness. What better environment to put it in. Air driers are available for just that purpose.> ...and doesn't need its corona discharge unit replaced, that it would be cheaper operating one bi monthly for the brief time it takes to nuke a 50 gallon batch of SW, as opposed to using Prime.  <Just aerating the water for 24 hours should neutralize the chlorine.> Thanks for the link, have read all through it ....<James (Salty Dog)> 

ORP Hi WWM Crew, It's me again in China with a strange ORP occurrence. I have looked through the FAQ and seen some answers to this, but wanted to just clarify if that's OK. After Xmas I fitted a C100 Certizon to the system and nicely it took the ORP from around 200 up to a setting level of 350 and all was fine. Then I did a major refit of the system as I wanted to remove the aggressive inhabitants of the system that were initially put in by the Chinese installers, against my wishes, but nothing I could do as it was done when I was at work, then to try and catch them to remove was not possible. I did try, several times. So I now have about a 140 Gall (Swimming area) system with a relatively small load, 1 Yellow Tang, I false clown, 2 Chromis, small goby and Dottyback, 4 shrimps, sea apple, tube anemone, carpet anemone, soft tree coral, a selection of 4-5 other soft corals, and a relatively small amount of LR probably 30lb. Now the ORP after the refit was in the mid 200's which I would have expected, so the ozone was on quite some time to get back to the setting of 350 in about 1 week. But now, the ORP is climbing on its own without ozone to a steady 460? <Yes... the ozone is "eating up" the materials that were keeping it lower... sort of like a fire if you will in a small space, that you're measuring the ash content of... without adding enough wood to keep the ash/wood ratio steady.> Everything looks fine and is doing well in the tank, the ORP drops immediately after my weekly 7 - 8% water change and then rises during the day again, all normal I think. But is it possible that now the bio-load has dropped quite a lot (Removed a total of 4 - spotted damsels, I yellow tail damsel, 2 - humbug damsels) that the ORP has a natural level this high? <Not really, or in many places, times... a good idea for you to "turn down" or cycle the ozonizer to keep the RedOx below 400... OR to add more life, food... am sure you understand the dynamic here> Really, really great info on the site by the way, fascinating and educational to read even just the daily questions. And what was that idiot on about yesterday with not accepting Bob's advice? <Got me> Great job guys and gals, it's so difficult to get LFS input as there is only one here!! Dave <Thank you for writing, your involvement. Bob Fenner>  

Ozone reactions Hi guys (Any girls?) <Yes, there are a few> I do not know if you remember, but I sent a message some months ago about setting up a marine system in Shanghai China. Well, to update you if you do, its been about 6 months now and everything seems to have settled down quite well now and the tank looks great. However, whilst back home in the UK over Xmas I brought a C100 Certizon ozonizer and ORP monitor. On return to Shanghai linked it all up and began slowly to add ozone to the system, its now fully cranked open after 4 weeks and am maintaining a level of 350. The water looks crystal, and most of the occupants seem to have adjusted to the water now, except my sea apple which has not shown its tentacles for about a week now, and the tube anemone which is only partially coming out of its tube. Is there a reason for this reluctance to emerge due to ozone and therefore drop the monitor level, or should I just wait longer to see what happens?  <Dave, in my opinion and ORP of 350 is a little high, especially since you don't mention filtering the return water with carbon. I would run this at about 300. James (Salty Dog)>

Ozone reactions Hi James (Crew and Girls Oops!!!), Thanks for the quick reply, but am a little confused as most of the reference books and generally on your site a recommendation of between 350 and 400 is normally stated as the target, and above this can be dangerous. <You may have misunderstood. I didn't know you were filtering the ozonized water with carbon, this is essential. Then, if you want to keep it at 350 ORP is up to you.>  For reference I have a 180G system with mainly sot corals, some live rock (difficult to get good here) and inverts. Fish= yellow tang, Dottyback, blenny, goby, clown, Chromis. Mainly small fish except the tang. My system being Chinese design is not the best, but consists of overflow box containing bio balls filtered before and after then into a 4 stage sump. Stage 1 now fitted with large Chinese skimmer, stage 2 & 3 coral stone and stage 4 fitted with internal pumps and heaters and a second small skimmer. I have placed carbon between 1st and 2nd stages of sump. Also fitted is ? hp chiller and a small 9w UV (Fitted before ozone system on advice of Chinese shop keeper, hmm), and now an ozone monitor controller. I also noticed since the introduction of the ozone that the large skimmer in stage 1 has produced nothing for about 4 weeks now, but before the ozone was producing about a cup a week or so. <Yes, the ozone is oxidizing the organics so you would see a reduction in waste.>  So my question would be: 1. 300 ORP reading after other readings, site seem to imply a higher level of 350-400. 2. The use of carbon in a mainly coral, invert system  <With ozone, outside of filtering the ozonized water with carbon to remove any residual ozone, is not really necessary.> 3. Due to the ozone going through the skimmer in stage 1 of the 4 stage sump, is the carbon on the outlet necessary? <As long as the ozonized water is going through carbon. Personally, I prefer Chemi-Pure over the regular carbon.>  Especially as there is some between the 1st and second stages although not perfectly sealed. 4. Should I de-commission the UV? <I don't think this is necessary either with ozone.> 5. Do you know anybody who would ship a clean up crew to China as they just do not do this here  <Probably cost you an arm and a leg for air freight. I'm sure some would ship.> 6. What is the weather like there, as it is very cold and wet in Shanghai? <I'm in Michigan and it's wet and about 30 degrees.> Best regards, Dave   <Good luck. James (Salty Dog)>

pH and ORP questions 2/11/05 Great site! ...and again, thanks for all the help and advice. <Glad to!> My 300g tank has been running for about 7 months, and I'm running into I'm sure some normal issues. I've got 5 species of soft corals (total of 15 corals), and they seem to be acting OK. Sometimes they will curl up (Lobophyton) or balloon up (colt), but I think they are going through normal respiration cycles. The next day, or even several hours later, they are back to normal. Maybe I'm wrong. I've got 4 yellow tangs, 2 clowns, 5 damsels, and a Dottyback. The fish act completely normal.  <Sounds normal.> The challenge is keeping pH and ORP up. I recently got a Milwaukee pH/ORP controller, and have frequently calibrated it to make sure readings are accurate. pH stays between 7.8 at night and 8.1 during the day. Way low, so I have been dosing Kalkwasser several times each day (2 qt RO water with 2 tsp Kalk dissolved for several hours). pH rises maybe one point with each dosage, but not much.  <This is a common problem. Have you taken a sample of your tank water outdoors, aerated it well and then re-tested pH? If it rises significantly, you have CO2 accumulating in your tank. This is common, especially in newer "tighter" houses that get less fresh air moving through.> Alkalinity is 16 dKH. I use Kent Marine buffer, which does raise pH, too, but I don't want to get buffer too high just to raise pH...therefore have been trying Kalkwasser.  <Wowza! Definitely discontinue any buffer additions, and check your calcium. You may have to add just calcium for a while until calcium and alkalinity are back in balance.> ORP is around 180 (day) - 190(night). Also way low. I just re-measured ammonia, nitrite, and nitrate, and all are 0. I've been doing 18g water changes weekly, and have been doing it twice a week for the last several. Yesterday, I did a 54g water change. Today, the ORP meter says 183. I'm using tap water because it is quite hard here in Phoenix. The ORP meter shows raw tap water at around 220. My RO water is about the same. I've been using Oceanic salt, but switched to Tropic Marin a few weeks ago. I'm thinking of switching to Instant Ocean to save on cost.  I do have some brownish algae on the gravel (not thick and fluffy, but just growing on the gravel). If I stir it up, the next day the algae is there again. I also have quite a number of little white tubular sponges growing in the shadowy places in the tank. I'm assuming all of this is from high nutrients/diatoms in the water, and would probably go away if I can keep pH up.  <The brown "algae" on the gravel is probably diatoms. Higher pH will probably discourage their growth, but they only require tiny amounts of silica, so trying to control them by limiting silica is probably futile.> I have an ETSS protein skimmer. I have to clean out the cup at least every other day because of the dark brown grunge that is collected. I assume that it is operating effectively. It's water is drawn from a surface overflow to ensure surface water is what is skimmed. A month ago, I introduced 7 ounces of carbon into the overflow that the skimmer effluent flows over, as well as the rest of the overflow water. I changed the carbon last week.  <Sounds good. With so much production from your skimmer, I wonder about your feeding regime. Does a lot of food go uneaten?> I've got 300lb of live rock, and a 4 inch aragonite gravel bed (not oolitic sand unfortunately, but the next grade up). There are 4 MAK4 pumps connected to a 1.5" "Anthony manifold" (you've got to trademark that :) ) that goes around the perimeter of the surface. I estimate water circulation around 4000-5000 gph. <Also sounds good. I will pass along your trademark suggestion to Anthony, though he is far too generous with his intellectual capital to even consider it.> The only thing I haven't tried is ozone. Please advise on how to keep pH and ORP up. Regards, Jerry  <Ozone has it's place, but you must also address the underlying issue. Perform the pH experiment described above. If the pH rises more than .2 units, try slightly opening a window in the room where your tank is and see how the pH and ORP react after a day or two. Also watch the ORP as alkalinity falls, as this may be affecting the result as well. Best Regards. AdamC.>

ORP, Quarantine Nitrogenous Levels elevated Hi to all the Crew<Hi Robbie, MacL here with you> Can any of you please fill me in on a couple of issues I need a little help with. Firstly I have a main 100 Gall FOWLR tank that I would like to connect to an Ozonizer via my Skimmer, Ozonizer is 200mg/h I do not have an ORP Meter as these are very expensive in the UK. Would this amount of ozone be too much to have on 24/7 or would I be better setting it on a timer to come on for say 1 hour out of every 2 or 3.<I would be very cautious about using something that you cannot monitor.  You are just running the risk of a catastrophe. Would be much better to wait until you can monitor it. Sorry.> Secondly I have a Regal Tang in my QT after an out break of Whitespot, (Been in there 10 days) the Tang is clear of whitespot and Cuprazine treatment finished 3 days ago but he does not seem to want to swim around just hides in the plastic Pipes (I put in the QT for just this reason) or lies on its side in the tank, the tank is a Reckord 96 with internal filter and power head and no matter what I do (5 / 10 Gall water changes every other day) I cannot seem to get the Ammonia 0.50 ppm and Nitrite 0.30 ppm down to zero (Could this be why my Tang will not swim around) the other problem is it does not seem to want to eat and I am just worried that it will wither away and die. <It could be the problem but it also might be a secondary infection left behind after the attack of the white spot. You might try a bit of MelaFix and do small water change every day to get that ammonia level down to zero.> I currently have Polyfilter in to remove the copper and I was under the impression this would also help with the Nitrite/Ammonia. <It will help some but it doesn't take it out like carbon does> Any help would be much appreciated

High ORP? 10/27/04 Hi Crew <howdy> I have a 120 Gallon Reef tank that has an ORP reading of 395 mV in the morning and 380 at night. <very fine/normal> I'm confident that the readings are correct because I checked the probe and meter with VitalSine ORP cal solutions of 240 mV and 470mV. In each case the meter reads within 4 mV of the test solution. I am not using ozone. PH is 8 .2, temp 79 Degrees F., Ammonia, nitrites, nitrates = 0. These high ORP readings please me and make me nervous at the same time. <huh? not clear on the interpretation of them as "high". These are quite normal in healthy tanks. Ozone can and will push them over 400mv... but this is not needed> I've read time and time again that readings above 375 mV are dangerous. <hmmm... I disagree here, or rather will state that over 425 is> Is a high ORP (>375 mV) dangerous if it occurs "naturally" i.e.: without ozone? <it is not dangerously high my friend... you likely have some/all of the following: heavy aeration, strong skimming, light bio-load and a good feeding/water change schedule. Best regards, Anthony>

Low ORP in new tank 10/13/04 Two weeks ago I filled my brand-new reef system with 2100 liters of RO water and mixed in Kent sea salt. I have had the system running since then with a 12 x p/h turnover, no livestock, no decoration and no filtration media other than filter floss so the water should be free from organic materials, pollutants and well aerated. Yesterday I added an ORP controller to the system and it reads 85mv. I would have expected it to be much higher. Is it normal to have such a low RedOx potential in practically sterile water or should I be looking for a pollution source / ORP controller defect? Thanks, Timon <the reading is not correct... all ORP probes need several days to break in (do re-read instructions for reassurance of this). You can expect a reading of 300-350 Mv likely. Do recalibrate the probe if a "normal" reading does not show after several days. Anthony> Water Changes & ORP To WWM Crew - This is an amazing site.  Thanks for all the wonderful and free advice.   <always welcome my friend> My question is:  twice a week I make water changes on my 125 gallon salt tank (1 ten gallon change on Wednesday and 1 five gallon change on Sunday) using buffered DI water that has aged 4 days.  Every single time I do this my ORP immediately (within minutes) drops almost exactly 150 points from 370-380 to 220-230.  This happens with both the five and ten gallon water changes.   <this is quite normal... it should recover within 24 hours> The ORP probe is at the opposite end of the tank from the sump return in which I add the new water - so it makes the rapid change even more puzzling.  The ORP gradually returns to normal over the next 24-36 hours.  The only creature bothered by this is of course me.  It doesn't seem to make any sense.   <understood... but it is normal/natural. The new water has not been exposed to great surface areas (turned over in low long tank) nor vigorously aerated as with a skimmer... and add to that the water change stirring up sediments that lower ORP, etc> Just to satisfy my curiosity - what is the mechanism or chemical reaction that causes this?  (I just bought an ORP probe a couple of months back and am no longer blissfully ignorant of the variations in ORP.)  Thanks! Scott <good thinking/curiosity... but no worries. Kudos. Anthony>

High ORP Readings I've read a lot on your site and I find it wonderful!  In fact, this is the second time I've requested help from you.   <welcome back :)> I now have a question about my aqua controller's ORP reading.  It's been operating on my reef for about a month.  I had to send it back about two weeks ago for some repairs in the logging portion but overall it's been great!   <agreed... ORP meters are a delightful means of monitoring water quality. Do not be concerned about the exact number per se (have a wide rage like 300-400mv), but instead use it as a tool to observe changes and shifts caused by changes in the aquarium (water changes or lack thereof, food types, etc)> When I first set it up, the ORP reading was showing in the low 100's and slowly, about 25-40 mV a day, it began to increase.   <this was an adjustment process... your actual ORP was never below 200 mv I assure you> I add phytoplankton and Reef Solution about every other day and that would always cause the ORP reading to drop on average 100-150 mV but after a few hours, recover.   <yes... exactly my point above. It help you to tune your handling of the system/husbandry. Do reconsider too if you actually have creatures in the aquarium that eat phyto (gorgonians, bivalves?)> I also add two part calcium as needed by calcium testing or about every third day.  When it finally reached 350 after about a week I felt no worries.  However, it continued to climb and now it is averaging about 500!   <not likely/possible without the use of ozone. A miscalibration> It still drops to about 350 when I add the additives but shortly recovers back up to this high ORP reading.  I calibrated the pH meter today and it is temperature compensated (Temp is calibrated as well).  ORP reading is pH compensated too so everything should be working right. pH varies between 8.3 and 8.1 day and night.  Temp is averaging between 77F and 79F - I haven't hooked these to the controller yet but eventually plan to.  It's been reading between 480 and 510 for the past week or so now. <again... not possible unless you are pumping a staggering amount of ozone into the system> I am concerned because I've read on your Redox page that anything over 400 can be lethal!   <Hmmm... rather subjective. For hardcore reef aquariums, even 425mv is quite safe IMO... although indeed on the precariously high end> However, nothing in my tank appears to be dying or being harmed; in fact it my corals are still growing like crazy.  Frogspawn, Torch are all splitting, Pulsing Xenia is growing taller and wider.  Other corals are doing well.  Fish include a pink spotted shrimp goby, purple Firefish, gold banded maroon clown, purple tang, & a mandarin fish.  I also have an arrow crab, peppermint shrimp, some scarlet hermits and some blue legged hermits and one sand sifting star.  I have a lot of those 3mm light grey looking two-four legged starfish all over. I have a 50 gal reef set up for over two years Four 55W 50/50 Comp Fluorescent lights ~90 lb live rock ~100 lb sand SOS overflow to sump with aeration drip plate and no bio-balls (water just streams into the sump and aerates very well) Heater in sump Sump Pumps to a chiller then back into tank via submerged ~1' multi-ported header pipe.   I have two Zoo-Med power sweeps in each corner of the tank for circulation and mild mechanical filtration with the suction sponge. The Neptune System instruction book says ORP should never need to be calibrated.  What do you think? <I disagree... no calibration is ridiculous. Although, I also admit that accuracy (calib) is not as important as precision (ability to measure change regardless of start and end points). No worries... the ORP meter is simply a tool for measuring changes and trends. The observation of a food causing a (for example) 40mv drop is far more useful than a questionable day-time high of 510 mv. Just monitor trends my friend and fear not unless you wish to harness ozone (in which case you need accuracy and precision). Anthony> Chris Bovia

Redox 9/9/03 Hello again! <cheers my friend> My new live rock has cured within 4 days! Ammonia is 0, Nitrite is 0 and nitrate is 5 ppm. I checked it again on day 5 and I had the same readings. Isn't this strange? <somewhat uncommon... but a good sign that your live rock was handled well> I have already read in the FAQ's session that it had happened to somebody else, so I do not worry much... <correct> My Remora skimmer is still producing a lot of dirty stuff. <yes... the more the better. And a very good skimmer too> I put a Polyfilter and some activated carbon in the sump to start collecting the dirt created all these days. Yesterday I put a couple of small hermit crabs just to see if they survive and to check on my Ammonia test and they are doing fine! Does this mean that I can proceed placing the sand and my first clean-up crew? <perhaps... but it would be better to run to at least 2 full weeks to be sure water quality is stable> My Redox is still at 415 (I do not use ozone). Bob has told me that it will drop while the live rock cures/ages. Is it still safe if it stays above 400? <yes... anything under 425 mv is fine> The live rock has 3 to 4 types of Caulerpa on it, which is starting to grow (some of it survived the trip from Indonesia), a couple of sponges and some other creatures that I am not sure if they are Aiptasia to Fan Worms. Is it a good idea to add a Peppermint shrimp soon ?   <not necessary... and they may kill more good things than bad. I'd leave them out> Is there a risk that except from the Aiptasia it will eat other live stock on the rock as well (the fan worms for example, in case they are this). <its more of a concern with them encroaching on other animals and burning them back. do try to chisel the anemones off the rock to be sure they are removed while there are few in number> I am thinking of leaving the tank with no fish for the next 3 weeks, because I suspect that I transferred Oodinium from my quarantine tank to my display tank using the same bucket. Is this long enough? <fairly safe, yes> Can I however put the clean-up crew (snails, brittle star and shrimp) ? Are crustaceans not infected by such illnesses? <not affected... but they can carry it> Sorry for the too many questions. Thanks a lot for the support. Thanassis <best regards, Anthony>

Redox Hello everyone! <Thanassis> I had my new 85-gallon reef running only with salt water for some time and the ORP monitor had a reading of 280 to 320. Two days ago I received my first box of live rock from Indonesia (about 45 lbs) and put it in the tank. After I placed it in the tank my Redox has been increasing constantly and today it has a reading of 400 ! I thought that the Redox should drop because the quality of the water is declining due to the slow curing of the live rock. Is this high reading normal ? Best regards, Thanassis <Likely so and nothing to worry about. The reduction oxidation level will slowly begin to drift downward with aging/curing of the live rock. Bob Fenner>

OZONE QUESTIONS-and a little help from the past FAQ's Hi Scott, I have one more... What exactly is ORP? <Oxidative Reduction Potential> I understand that skimmer increases ORP, which is good. But why certain people employ ozonators to increase ORP? Isn't skimmer good enough?<Do read below> Can ozone be dosed directly into tank, or does it need some kind of special chamber? Is it better than UV light at fighting pathogens?<Inject ozone through a proper reactor or skimmer and pass all effluent water over activated carbon, and change the carbon regularly---UV is used germicidally to reduce the numbers of pathogens (but no guaranteed cure, mind you). It is simple and safe but requires very regular maintenance to be effective... needs prefiltered and clear water clarity from chemical filtration regularly), bulbs need to be changed every 6 months (they are dear in price) and the reaction chamber needs to be cleaned/flushed at least monthly. Ozone on the other hand has numerous benefits: germicidal, adjustable, imparts oxygen to water, improves clarity (clears discolorants to reveal icy blue water, improve Redox potential of the water (indirectly inhibiting algae) and more. However, it can be overdosed if not controlled. Must be used with a controller or at least watched with a Redox meter. Effluent water must be passed over carbon changed regularly. With extreme misuse can be a slight to moderate health hazard to people. If you are moving fish in and out frequently, or if your system has a heavy bio-load, I'd suggest an electronic (not corona discharge) ozonizer with a Redox controller and carbon chamber. If you are a casual aquarist with a central system that will not see frequent new entries (w/o quarantine)... then a UV may be safer and satisfactory.(Found this on the WWM...by Anthony Calfo :)> Thank you, Luke

ORP level for controlling Ick?  5/103 Wet Web Media Crew Hello, I have a reef tank 500 Liters, and I'm using Aquazone 100 mg With ORP Controller, What I would like to know - How high should the ORP level be if I would like to Kill \ Weaken the ICK? thanks in advance,    Asaf. <there is no direct/correlative reading of ORP for controlling parasites. Disease control begins with proper quarantine of all new livestock in a separate vessel for 4 weeks prior to entry in the main display. That said... a good Redox value with ozone in the aquarium is around 400mv (350-425mv range). Stability is better than occasional spikes to unrealistic highs (some folks push ORP to 450mv or higher). Best regards, Anthony

Re: Clownfish question Thanks again last week for your help with my Redox question. For an update my PH was ok but because the volume of my water changes were too small so my Calcium and Magnesium levels were low therefore my Redox went up. I did a larger water change and my Redox is now at 409mv. I will do another water change next week to try to get the level between 350 -390mv. <Cool! Glad Redox is where it needs to be and your calcium and mag are normal!> Anyway I have another question that I hope you could help me with. My tank is 135gal and since it has been setup last June I have had a pair of percula clowns and a host anemone. I was at the LFS last week and saw a nice carpet anemone (haddoni) with 2 saddleback Anemonefish in it and I plan to pick up the anemone tomorrow and I was wondering if I bought the saddleback Anemonefish as well should I expect a huge battle between the new ones and my Anemonefish now? <Yes, and perhaps to the death, I wouldn't advise...  Also, are you aware of the potential size of the carpet anemone?  How wide is your 135?> They would both have there own separate anemones but would that be enough? <Nope.> Any help you could provide would be greatly appreciated. Sincerely, John Perry <Hope this helps in your decision! Plan carefully!  Craig>

Redox help Dear Mr. Fenner, My name is John Perry and I have a Redox question that so far I haven't been able to find an answer to.   <Okay.> Last June I setup a new 135 gal overflow system with a big Berlin protein skimmer. In the beginning I had a high RedOx value at about 500mv and the local fish guy said that my water was too clean so I should either remove some of my filter media from the sump or put in more fish, I chose to do both. When I did my RedOx went down to 350mv so I was very happy.   <High RedOx is an indicator of good water quality, why on earth would you be encouraged to lower it, and thus the indication of water quality? Have you searched on Redox (oxidation reduction potential) at WetWebMedia.com? This is the most basic information about RedOx, it would be advisable to find out more!> But about a month ago my RedOx value started to climb again bit by bit everyday almost. When it got to about 400 mv I turned off my skimmer but its still climbing and today its 490mv.  On the internet the only thing I've been able to find is how to raise the value not lower it so I'm at a loss as to what to do. <This is because higher is better, not the other way around. Do understand, high RedOx levels of over 450mv are common in well-oxygenated coral reefs free of nutrients, and less than 200mv in nutrient rich lagoons with lower oxygen saturation. Your skimmer should run 24/7 and a constant RedOx level of 350mv or higher is desired. Redox levels are an *indicator* of water quality. Falling RedOx indicates a water quality problem, a higher RedOx indicates good water quality. You may want to check your pH to make sure your elevated RedOx isn't from a depressed pH. You should shoot for a consistent level.  When it starts to fall then it's time for maintenance or to look for reasons for water quality degradation.> Since the setup I've only changed the water twice including yesterday where I changed 15gal and I haven't cleaned out my filter at all. If I clean my filter media will that remove some bacteria therefore reducing the RedOx level? Any help you could provide would be GREATLY appreciated. Sincerely, John Perry P.S. I love your book "The Conscientious Marine Aquarist" it has been indispensable and has helped me learn a lot, thank you! <Do read up on RedOx potential before worrying about higher levels. You have been mislead by your LFS to think lower levels are desirable, this is not the case. What you want is consistency and no big swings higher or lower. Levels over 350mv are adequate. I suggest getting the pH meter as well.  Best of luck, Craig>

Re: Redox help Thanks a lot for your quick reply, I really appreciate it. I was concerned because in all the information I could find on the net including wetwebmedia.com said that RedOx readings over 400mv were dangerous to life I was wondering in what way is it dangerous,  so that's why I was getting worried. I'll go and check my PH maybe it's out of whack. Thanks again for your help. Sincerely, John Perry <Glad to help John!  Let us know how it goes! Craig>

Follow up, High ORP Guys, as to my question about the high ORP of my reef tank ,450 gal plus 90 gal refugium, not overstocked with fish, not overfeeding. <understood> I thought 350-390 was an ideal range, what range should I be comfortable with a set up like mine, thanks Paul <You are correct, Paul. 350-390mv is a fine range. I take no exception to that (see first message pasted below, "yes... agreed 375mv is quite fine"), but rather.. I am concerned about the statement that your Redox has leveled higher than the set point (!) and climbed as high as 432 even with the airstones off and even the skimmer off for 2 days!! That is a problem... its not even possible. You have a malfunction with your Redox meter/probe, my friend... experiment until you determine the cause. Best regards, Anthony> ORP unnaturally high? Faulty meter Guys, my reef setup, 450 gal plus 90 gal refugium is doing fine except for one mystery. I  have been running an Aquazone 200 mg for 2 months and the ORP stabilized at about 375, <holy cow!!!! How much of that 200mg are you running?!?! That is way too much for a tank this size unless you feed very heavily or the tank is overstocked (requiring the heavy ozone). And keep in mind that the mfg telling you what size unit you need is also trying to sell you something ;)> the value I had set the unit for. <yes... agreed 375mv is quite fine> Slowly, even though the unit was not producing ozone, as shown by the ozonizers indicator light, the ORP reading was rising. It is now at 420,but has hit 432. <unless you have an extraordinary skimmer (RK2 or the like) with massive, almost pressurized oxygenation as well as frequent water changes and heavy chemical media... I would doubt this reading. Redox does not climb easily for most any system. Unnatural> I have adjusted the ozonizers settings to minimum, thinking the indicator light malfunctioned, ORP stayed at approx 420,turned of my airstones, no change, even shut off the EuroReef cs12,for a 2 days. <awesome skimmer, but yes... your ORP should have dropped measurably as soon as the skimmer was turned off if nothing else. This unit is misreading for certain> Tank looks great, should I be worried? Thinking the electrode or unit could be faulty. <agreed... or something else. Feeding, lack of skimming and simple time (hours) will bring down the ORP. We have faulty equipment here> I have not changed anything else, same feeding schedule, etc. Thanks for your input, Paul. <best regards, Anthony>  

Porcupine puffer / Ozone question (really, quarantine, Redox,) Hey Bob, I have been reading through your FAQs and Puffer information but didn't see anything relevant. It may be nothing. 125Gallon acrylic tank, Sea Life 150 Wet/Dry, Sea Life 75 protein skimmer, a Rio 2500 as a return pump (is this too low for a 125?), <If it suits you, your livestock's needs, no> and as of 3 days ago a Red Sea 200mg Ozonator + Redox controller. ph 8.2 salt 1.022 <I'd raise to about 1.025 over a few weeks time> ammonia - 0 nitrite - 0 copper - 0-0.1 <Where is this residual copper from?> I'll go into detail a bit more after the initial question. I just bought a porcupine puffer (common one with the flat laying spines sorry I forget the sci. name) <Please see WetWebMedia.com re... most common species listed, illustrated> I let him float for about 10 min, and added him to the tank. Not wanting to add LFS water to my tank, I dumped him to a net and released him to the tank. (I know not the best way but no option really at the moment).  <Quarantine...> He didn't puff or anything, but after about 5 minutes in the tank, his spines on the top of his head only in the front, maybe 5-6 spines total, stood up on end, even thought he was not puffed, a few here an there around the rest of him did this too.  <This happens... sort of like our erector pili muscles and body hair...> The first thought was residual ozone in the water (I bought a chlorine test kit the other day to check for ozone (I read it acts the same) and it came up 0), so I immediately unplugged my Ozonator. Since then the tank lights have come on, and he's just kind of hanging out, laying on rocks and corals not moving much.  <Typical> (lol just went to look at him to check his breathing and when he saw me he held his breathe it looked like, anyway just turned the lights out). He looks healthy, no spots, nothing off, breathing normally as near as I can tell. What can cause the spines to stick up like that? <Perception of danger> Some tank history / etc. The tank had been setup for almost a year (using tap water), with a clown trigger, spotted dogface puffer, 3 green Chromis and a blue damsel.  <Yikes... maybe the Clown Trigger... they can/do sometimes eat puffers (and all else) in the wild> About 2 months ago I moved, got the tank setup again and livestock added back in in an hour or two. Everything was great, but I wanted a new fish.... 125 gallons with 2 fish and 4 damsels seems awfully light. So I added a yellow tang (whoops). The tang was scratching, but I ignored it, then one day I saw the spots on him. The clown trigger was the first to go. In the next 4 days (2 FW dips a day and copper added) all the fish in the tank were dead other then the damsels (I successfully offed them a few weeks later due to stupidity).  <...> So, tired of losing fish, I ordered an Ozonator (200mg) Red Sea with Redox probe and controller.  <An effective quarantine set-up and protocol would be cheaper, more effective.> I added it to my Sea Life 75 skimmer (venturi), and after 5 minutes could smell ozone in the house. DOH ! Forgot the carbon for the air!! So back to home depot and after an hour in the PVC isle, I find the pieces needed to get all my air lines to vent through carbon (I hope, don't smell it in the house now just under the stand). Then I read about running the water with ozone through the carbon, not over (as I had been doing), so back to Home Depot, I bought more PVC and glued together a canister with holes in the bottom and a bag of carbon in it, for the skimmer to dump over. I know I need a residual ozone test kit, no one local has them. Should I leave the Ozone off?  <Yes... or turn it down to about halfway... 100 mg./h should be no problem... you would likely see change in pH if there was excess...> Could these spines sticking up be from the ozone, or just the stress of acclimation? Return pump is good enough? <Could be just stress of handling, capture... I would check dissolved oxygen re pump adequacy... and if, when in doubt, add more circulation...> One more big question, the ozone has been on for about 3 days now, I've had it all the way to 125mg, but backed down to 50mg/hr now (actually off now cause of the puffers spines sticking up) So I know it takes a few days for Redox to get up there....When I put the probe in the sump, it read 150. It went up to about 160, and now is back down to about 130 (morning it should be a little lower) Will it get up to 300 eventually with the ozone on?  <Perhaps... due to feeding, other life, metabolism in the system... but maybe not...> Why is my Redox so low even without ozone or anything I would of expected it 200+!  <No... it is... what it is... and not surprising for captive systems.> I thought I had a healthy tank. It has been tap water, though as of the last week I ordered replacement filters for my SpectraPure! So yesterday before I even bought the new fish (today) I did a 25 gallon change with the RO/DI water using R/O Right by Kent and Kent sea salt, and a little PH buffer (recommended amount for 25 gallons). Any useful info you have about this all would be great!  <We need to start... much further back in your history here and period in the hobby... Many factors go in to "proper set-up" and Redox potential is a measure of "charge potential" in a system... with all that has gone on (addition of medicants, dying livestock...) it's not surprising that you have low Redox potential...> I am kind of thinking the tap water has a very low dissolved oxygen potential, <What? This doesn't make sense... the water can only hold about 7 ppm. of oxygen... it can lose or gain this in minutes... by just being shaken in the air, turned over...> due to my 75 fresh community tank slowly kills fish (sort of really just my 9 Neons are now 2, but I caught a Cory at the surface for awhile breathing heavy) I guess I could put the Redox probe in the tap water?  <You could> What should tap water Redox at? <Whatever it is... likely 200-300 microSiemens per... Not important variable for potable consideration.> Side tank history/story...Due to the tang whipping me out, I since setup a 20 Long as a QT.  <Oh... good idea> Using a Duetto 100 for a filter, and a small mini-jet powerhead (no air bubbles in the tank ugh salt creep ! and no skimmer, its just a QT temp tank). That's where I moved my damsels from the main tank (they always eat my puffers tails!), so a day or two after I set it up I decided to test the water...no ammonia or nitrite, but the pH is like 7. Ok that's why the fish are stressed, low ph!  <Definitely one aspect> I figured the am an no2 (nitrite?) were low due to the sponge an water from the main tank. So I buffered (way over buffered the PH) back to like 8.2. In an hour <Too much, too fast...> the damsels were dead :( Being a new tank, I left the dead damsels in there for a few days before removing the remains, I tested the water in there yesterday and the ammonia and nitrite were both off the scales (good here comes my bacteria already!) Point of all that, was does my QT setup sound ok? <I would add an aerator... a bubbler... likely in the way of a sponge filter (or two)... that you could "culture" in part of your main system for immediate use...> What size fish can it handle for 20 days? I'd think it'd be ok as long as nothing is over 6-8" in size. <Depends on the species, their behavior... but about this size> The puffer is the first and only fish in the main tank since the whip out, tank sat empty for about a week (not empty just fishless) while Ick died off. <Needs to sit like this for a month... w/o fish hosts, with elevated temp., lowered Spg. per what we have posted on WWM> Really concerned about the Ozone and Redox. It was an expensive purchase, and I know it can really increase my water quality and Redox (135 now), <Please read what is posted on WetWebMedia.com re quarantine, Redox, ozone... use the Google Search tool posted on the homepage, indices... with these terms... what you need to know to understand more completely what you are doing, not doing, is posted there...> I just want to make sure I'm doing it right and all that. I bought a chlorine test kit the other day to check for ozone (I read it acts the same) and it came up 0. <Not the same...> Thanks in advance! going to read more of your site now!! <Good. Bob Fenner> Mark

Oh yah... The spines have since laid back down, I have not resumed the use of Ozone till I hear back from you or at least get a residual test kit. Spines laid back down about 20 min after turning off the ozone. (may or may not be related) <Not related. Bob Fenner> TIA again! Mark

Oh yah... (Puffer, ozone, Redox...) Thanks for the reply. The puffer seems fine today, and I turned the ozone back on at 55mg/hr last night after reading all of your ozone FAQ's. I must say, GREAT site, you guys have an amazing wealth of knowledge. <Glad to share> 125Gallon acrylic tank, Sea Life 150 Wet/Dry, Sea Life 75 protein skimmer, a Rio 2500 as a return pump (is this too low for a 125?), <If it suits you, your livestock's needs, no> I am would like to do maybe 4 fish total. The puffer, an angel of some sort eventually, probably a wrasse of some sort, and something else. Does this setup sound ok for the 4 fish or maybe even 5? I know the Angel and Puffer will get big eventually. <S/b fine... if they're small enough, compatible> The 0.1 copper level is residual. When I had the ich whip out my tank a few weeks ago I added copper for a week, since the fish died I didn't bother keeping the copper level up. <Look into Polyfilter, GAC use to extract it> Yes I have the QT tank setup, but its not ready for fish, the puffer being the first and only fish in the main tank, I didn't think the QT was a big deal for this first fish. <<Mmm, yes... you don't want to have a "parasitic tank"... the tank itself can become infested...>> <Yikes... maybe the Clown Trigger... they can/do sometimes eat puffers (and all else) in the wild> It was the green Chromis picking on the puffers tail (old dogface) near puffer is alone in the 125 gal. <<Okay>> <Could be just stress of handling, capture... I would check dissolved oxygen re pump adequacy... and if, when in doubt, add more circulation...> The only circulation in the main tank is the return from the RIO 2500 in the sump, which is a spray bar aimed at the surface, should I get another power head in the main tank to just turn over water? <<Yes... I'd get two>> Will it get up to 300 eventually with the ozone on? <Perhaps... due to feeding, other life, metabolism in the system... but maybe not...> Why is my Redox so low even without ozone or anything I would of expected it 200+! <No... it is... what it is... and not surprising for captive systems.> There's only the 1 fish, even with no fish it was only 150...was at 135 when I checked before work this morning. I'll let it be a week and see... <<Good>> <We need to start... much further back in your history here and period in the hobby... Many factors go in to "proper set-up"> Any specific info? Its a 125Gal tank, that started with live rock. The rock then sat in a bucket for 6 months with no circulation when we had house work done. During this time the tank was empty. I added the rock back in and let the tank cycle a month with 4 damsels. Then I added the clown trigger and dogface puffer, all was well for months, even till after I moved, just when I got the yellow tang without QT and got bad ich. I realize the rock is no longer live (especially after a copper treatment) but it should still be ok as rock for looks right? <<Yes, and will become repopulated... add a bit of "new live rock" over it>> The 125 Gal. tank has an overflow skim box, that drains to the SeaLife 150 wet dry. There is 1 heater in there (after reading your heating FAQ I will add another soon). There's also a mini-jet in the sump simply moving water to prevent the surface from getting 'stagnant'. The water then drains through a bulkhead with a ball valve, to another smaller sump. In this sump is the Sea Life 75 skimmer injected with ozone, and dumping over my homemade carbon container, and the RIO 2500 return pump next to it. The water is then returned to the tank via a spray bar that does a pretty nice job cutting up the surface on that side of the main tank. I had been in the industry about 6 years, and thought I had a pretty good idea on how to keep fish, albeit some stupid mistakes (like raising the ph in the QT so fast) and being out of it for a couple years I don't know now, also expense I know I could use a larger skimmer, but the Sea Life 75 has never really worked that hard and pulled that much nasty from the tank. I was thinking of going to a Sea Life 150, but these skimmers are difficult to incorporate with Ozone (due to the air coming out) Any suggestions on ozone friendly skimmers if I wanted to get a bigger one? In sump model. <<Look to the Aqua C or Euro Reef lines>> Anyways thanks again for all the help and support you've given the industry, some day if I can get my own fish to live I'm really thinking of trying a store/service shop, especially after seeing the immense store and what not Dallas North Aquarium has become over the last 6 years. <<The trade needs people with drive, curiosity, positive helpful natures... Bob Fenner> Thanks again! Mark

ORP Mystery Hello Bob Fenner and crew. <<Howdy!>>I have a 250 gallon salt water tank which has been in operation some two years now. Great hobby despite the ongoing trials and tribulations but, that is what makes it fun I guess. A voyage of discovery no doubt. The tank is 48" tall 36" wide so I guess it fits the definition of the dreaded show tank. The tank has never run a super high ORP and tended to settle in the high two hundreds (275 or so) even with the addition of a small amount of ozone through the skimmer. About two weeks ago the ORP took a nose dive to 220 or so. Checked circulation. Same as always. No missing headcount which might be a loss fish fouling the system. Further research on ozone systems indicated that the CD tubes that produce the ozone are only good for a year to 18 months. Was using a Red Sea unit rated at .2 grams per hour but usually ran it at .1. Replaced the unit with a Clearwater since it has provision for easy CD tube changes rated at .3 grams per hour and have been running it wide open for about 24 hours now. ORP still stuck at 225 or so. I have tried 3 different ORP probes on two different meters and all confirm the 220 or so ORP reading. Sand is clean and while there is no obvious build up of other material.. Live stock seems to be doing OK but with some labored breathing noticed. Any ideas? Stumped in Vegas <<As you know ORP is only an indicator....I would break out the dreaded test kits and have a full look. There is something wasting or building up somewhere. (that's why you have the ORP to begin with) Start with your make up water and proceed step by step. It doesn't sound like your ozone. Labored breathing would lead me to testing ammonia, nitrite, nitrate, pH, etc. Give this a try and see if you find it. Hope this is it, Craig>>

Continuously injecting ozone Thanks for the previous responses. I have a question now about injecting ozone into my skimmer. I have a fairly large Beckett skimmer (40"), that has a lot of swirling/agitation/etc, so the ozone should all be worked off. <Not necessarily.> Right now its connected to an ORP controller for 350mV. There is carbon in a chamber post skimmer, so that helps as well. <These two do more than help, they work very hard to ensure that no residual ozone makes its way into your tank.> I'd like to continuously inject ozone into the skimmer chamber, rather than off/on which it is doing now. Even if the ORP is at 350 right now, is it feasible/safe to constantly inject a low amount of ozone into the skimmer (like 60-75mg)? <No> Will this raise the ORP too high? <Yes, and then burn/melt/oxidize your fish.> How can you consistently shoot ozone into a system when the ORP is already high? <Not a good idea.> Is my water quality/ORP staying high which is a good thing? <Yes> and injecting more just isn't worth it? <Isn't worth the risk.> Thanks, Jim <You are welcome. -Steven Pro>

ORP Hi! There, <Hello> I hope all is going well. This time I have a question about ORP. <Okay> I have a fifteen hundred gallon system that has been going for about three months now. I started off with a specific gravity of about 1.018 and then did a 100 gal water change last week. The SG is at 1.0195 now. It seems that the Ph has dropped just a little bit (8.08-8.24) now. Also the temperature dropped a little bit as I moved up my halide lights. <All to be expected> However what is puzzling to me is that my ORP readings are between 390-410. That seems so high. They used to fluctuate between 350-395. Please tell me if my ORP probe has gone bad and I need a new one. <Mmm, you might well want to "test the tester" here. Don't know if the probe is off, or your meter... but would try another tool><<Is/was likely just the boosted photosynthesis-effect. RMF>> I know ORP is connected to a variety of things like Ph, Temperature and many other parameters but I am concerned because of the change. At what point do I start to get worried? <Never worried my friend. Concerned and directed enough to direct your actions toward safeguarding your system and enjoying it. Bob Fenner, who would be concerned if the RedOx potential shifted more than ten percent in a given hour to hour in a day frame (let's say Tues. at noon compared with Monday at noon), or if the RedOx dropped below 350 or so... definitely would be looking for remedies anywhere near 300...> Thanks again, Bhaskar.

EC/TDS Meters Mr. Fenner, I purchased a Milwaukee Model SM301 Conductivity and TDS meter, but found that it has very limited instruction on how to read and define the meter reading. I was wondering if you might have any knowledge of this. The following are some of what I am looking for plus any other info you can offer. <Hmm, would contact the Maker: http://www.miltestersusa.com/  re better, more instructions... and/or the folks who sold you this gear.> Meaning of mS/cm? <micro-Siemens per centimeter... a "new" standard of conductivity measure equivalent to "micro-ohms per centimeter"... the company "Siemens" IS that big, influential"... A higher reading indicates more ionic content, higher conductivity...> The range of the unit is 0 to 1990 mS/cm. What is considered a normal reading? <Normal for what? Marine, brackish, freshwater, Koi ponds, water for epiphyllums...? Again, I would, will cc Milwaukee Instruments here... Bob Fenner, WetWebMedia> Leldon

Aqua Medic Products I am reply to your email from the Aqua Medic USA office. Your email was forwarded to our email address. From my readings you are looking for an Redox computer with a probe and some Deniballs. Do you live in Australia? Aqua medic, USA 281-419-0086 Phone <Ah, actually, this was/is a forwarded message from a request to our site (WetWebMedia.com). Please refer to the original message for the originators name, e-mail address. Bob Fenner>

Ozone and Redox Controller Per your advice in the Conscientious Aquarist I recently purchased a small ozone generator RedOx controller combination for my 250 gallon tank. After two days the results are outstanding (I think) with perfect water readings and crystal clear slightly bluish water it looks like you could just walk through it is so clear.  <Wowzah, quite a description> Here is the dilemma. When I first started the controller I had a RedOx reading of only 95-100 mv. (Whew, didn't think my water was that bad). After two days on low to mid levels of ozone (5-10 ml per 25 gallon)  <Let's make that milligrams of ozone per...> the water looks great as described above but the RedOx reading is only 108-109. I turned the unit up slightly but after another 12 hours only hit the 109 number. I could continue to increase ozone but am reluctant to do so since things look and fish behavior is so good.  <Don't blame you... the livestock is the best, grand arbiter of "how much is enough"> Tried the probe in a slightly aged batch of fresh artificial sea water and could only get a 92-98 reading. Does that seem right for fresh sea water with no organics at all?  <Hmm, no... should be 250-300 plus microSiemens per centimeter... depending on mix, source water...> I am beginning to suspect the probe/controller may not be accurate.  <Me too> I do have some slight residual copper from an earlier treatment but don't know if that would effect it either. <Nah> Have ORP test solution on the way but would sure appreciate your thoughts. <Have your probe probed... check the checker...> Thanks as always <Be chatting. Bob Fenner>

ORP too high? I am a faithful daily reader of this column and I truly appreciate all your excellent advice. My question relates to ORP - specifically if it can be too high. My new tank (not my first) is 180 gallon regular with 220# of M.I. live rock, 125# live sand. This is my equipment list: 2 175W 10,000K Metal Halides, 2 55W PC white, 2 55W PC actinic, 1/3 HP chiller with dedicated Iwaki MD 40RLXT pump (on/off w/ chiller), Iwaki MD70RLT main pump, ETS Gemini 800 Skimmer w/ dedicated Iwaki MD55RLT pump, K2R Calcium reactor. Lately, to avoid overheating/overskimming the tank and save energy costs, I only have the skimmer on for the 12 or so "night" hours. The waste produced by the skimmer seems to be about the right amount, based on my past experience with downdraft skimmers. The ammonia and nitrites are zero, and the nitrates (w/ a reef test kit) are about 3 ppm (correct scale? where <10 is good). I control everything with a Neptune Systems Aquacontroller. When I first set up the tank a month ago, the ORP hovered around 300-350mV. Now the Ca reactor has been going for about two weeks, and my ORP has gradually climbed up to about 425 mV. This may seem silly, but should I worry about the ORP being too high? I do not use ozone. The probe supposedly does not need to be calibrated. I moved the probe around different "sides" upstream/downstream of where the CA reactor doses into the sump and get about the same reading. I don't think the ORP probe (brand new) is too close to either the pH probe or the grounding probe. I run the reactor at 55-65 bubbles per minute, with effluent flow of about 30 ml/min at pH 6.6, all as recommended by the manufacturer. The pH in the tank is rock solid at ~8.2-8.3. Is my ORP really this high? Is this OK? Should I be happy about this? All my fish and all my corals look great, but I just wanted to see what your opinion might be. It just seems weird... >> Hmm, not weird at all, and very beneficial... Yes Oxidation Reduction Potential can indeed be too high... but depending on the actual "cause(s)" anything up to about 500 micro Siemens per centimeter (I think the next change in units ought to be micro-bobs...) is okay... Am a little curious about any measure of biominerals in this system... i.e. you may be a little high on driving the CO2 through your reactor (bubble counters are notoriously "inaccurate", "imprecise"... they just don't give an "average" count that means much at times...).  Anyhow, for our general understanding here... and in perpetuity (love the net!), you're adding charged particles (Ca++ and more) to your system... increasing its conductivity (the indirect way that ORP is measured... right? as in the units it's measured by your meter...), increasing the ORP respectively... Does this make sense? Think back to the James Bond film where he throws an electric fan in a bath tub with the bad guy... Would you rather it was a tub of milk? distilled water? Or your system with the reactor turned up? Take the milk... non conductive, then the distilled. Bob Fenner, who REALLY likes calcium reactors and CO2! 

ORP drop with water changes????? Bob: This has been bothering me for some time, and I can't figure out why it occurs. Every time I make a water change (done with ro or deionized water, mixed and heated properly, allowed to stand 48 hours or more before actual change, 35 gallons changed out of a 180 gallon tank at a time), my ORP reading on my computer plummets a hundred points or so and takes a week or two to improve. Generally coral polyp extension improves immediately, water appears clearer, in other words all visible signs look good. If I have decreased the amount of particulate and dissolved organics in the tank, why would the ORP go down and not up? >> Well, the answer is quite... simple: and with apologies to the folks at Tumwater, "It's the water, and a lot more". Think back to your early chemistry classes. (Geez, I used to teach the physical sciences at the HS level...). Remember that RedOx, oxidation-reduction reactions (aka acid-base) are a type that involves the loss or gain of electrons (the ever useful acronym OILRIG, "oxidation is losing, reduction is gaining"... electrons)... Now, when you're changing water a bunch of "things" are happening, but one overall reaction type that registers on your meter... the combination (read that as neutralizing) of existing organic acids in your old water by the mix of mainly alkaline minerals... Ahhh, hence less conductivity, hence lower ORP reading... but as you know, not really an indication of "viability" of your water... A danger of aquarists/humans relying on a point, as a reference... and a useful illustration of the subjectivity of the human experience, eh? A pleasure, as always. Bob Fenner

Question: Hi Bob-I have a 240 gallon set up with a deep (6") sand bed. Circulation is about twenty tank fulls an hour. My trouble is that without ozone I cannot get my RedOx readings above 250 mv.-with ozone (Sanders unit set at 200 mg./hr. through venturi in Tunze skimmer) I can reach 370 no problem and everything looks great. However, I am worried that the ozone is depleting some elements and perhaps harming some corals (mostly LPS and soft). Alkalinity is 3.5 mEq/l, sg. 1.026, temp. 79. Few fish, no feeding. Is my sand bed degrading the tank environment with excessive BOD? thanks for your input.

Bob's Answer: Hey Kurt, no real worries with ozone induced readings... The reductive environment in your humongous sand bed NNR is no doubt having an effect, but not one I'd worry about. I would run the ozonizer, and not worry a wit re: RedOx effects here. Don't think you have an excessive biological oxygen demand (this would show up in a few ways in your tests and be observable re: your corals...). Do you utilize Ca supplements or CO2? All in all, if "it ain't broke" (and I don't see that it is) I wouldn't fool with it (you may quote me).


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