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FAQs on Marine Water Quality involving Phosphates, Measure

Related Articles: Phosphates in Marine Aquarium Systems by Marco Lichtenberger, Phosphates in Carbon; An analysis of the phosphate content of activated Carbon by Steven Pro, Ammonia, Nitrates, Nitrites, SilicatesMarine Chemical Filtrants,

Related FAQs: Phosphates 1, Phosphates 2, & FAQs on Phosphate: Importance, Science, Sources, Control, Chemical Filtrants, Troubleshooting/Fixing, & Nitrates, NitritesAmmonia, Silicates, Avoiding Algae Problems in Marine System, Nutrient Control and Export, Algae Control, Marine Maintenance, AlkalinityChemical Filtrants

Using different assays, test kits, "your results may vary"... And do bear in mind that available phosphate is a dynamic condition... all can be "bound" by life at some moment, released to extents at others.

Phosphates. Measuring zip      5/24/13
Hi Crew,
I run a marine tank which is about 18 months old and heavily stocked with fish which are all very well  and I do not normally test for Phosphates but as I want to add some inverts so I tested for Phosphates with a Salifert test kit and they showed virtually Zero. Not complaining but is this normal?
<It certainly can be. Good food/protein skimming/water changes/"aquascape" can all contribute. -Nate>

PO4 "trapped" in LR & LS -- 02/12/10
Greetings Crew & thanks a million for this web site.
I have a 90g reef. Params are currently CA 400, Alk 3.2, NO3 <1, Ph 8.4, Amm Nitrite 0, SG 1.024, Temp 79. Have a 1200 gph pump, 2 Koralias, TurboFlotor blue skimmer, 75g wet/dry filter & UV sterilizer. Lights are 520w PC's
LR & LS have been in tank 3 yrs.
<I'd be switching out, adding some new.>
There is about 80# LR & LS is 2-3" deep. 2 weeks ago I added some new LS & stirred up some of the compacted bed. 3-4 wks ago I changed PO4 media from PhosPure from Drs F&S to RowaPhos in a fluidized reactor. H2O changes are done 10g/wk. Green film algae & some red Cyano are growing on the glass, sand & small places on the LR. This seems to have started about 2 wks ago.
PO4 levels in the H20 column are <1.
<I hope so... better below 0.10 ppm>
Within the LS & LR however the PO4 levels are much more like 5.
<Zounds! How's that look? Sound?>
Why isn't the RowaPhos removing PO4 from the substrate & LR, or is it just a slow thing?
Doug from MI
<Can't tell from here. I'd first be checking your test kit against a standard, other reliable assay. Bob Fenner> 

Re: PO4 "trapped" in LR & LS -- 2/12/10
My mistake. PO4 in the water column is less than 0.10, i.e. no blue tinge w test reagent.
However, with a few small pieces of chipped of LR in the test vial w 10ml of tank water, PO4 is 1-2 ppm!!
<Mmm, not too much of a worry... unless there's a whole bunch of "chipping" going on in the system>
So, should I toss a few pieces of LR that don't have corals attached & replace w new cured LR, or is there something that the RowaPhos is not doing??
<Likely all is fine here. I would take a/the long-term approach... look into expanding/adding a live sump, large DSB, RDP macroalgal culture... As gone over and over on WWM. Cheers, BobF> 

Detection of phosphate levels in reef aquaria using photometer, variances in readings  10/20/07 Hi, <Hello> My apologies for resending this email but I see on the WWM FAQ page that if a query goes unreplied for over 24 hours that it is sometimes worthy of checking to make sure that it was received. Apologies if you have indeed already seen this question, but if not, here it is being resent. :-) <No worries. I don't recall seeing this> Thanks for your time and trouble! -- Tony Slotboom Hi WWM Crew, My question pertains to the measurement of phosphate levels using a handheld photometer (Hanna Instruments make a low-range phosphate meter that has recently been gaining popularity among aquarists). Other than recognizing that "lower is better", and that it seems generally accepted that as reef aquarists, we want phosphate levels to be 0.04 "or lower" - I'm finding it a bit hard to find abundant metrics on what constitutes as "normal" or "average" phosphate readings in reef tanks. Part of my issue is that the tester itself that I'm using, is subject to variances of "plus/minus 0.04." So if I take multiple tests of some tank water, I may get readings from 0.00 ranging up to 0.03. To be sure that I wasn't introducing error by following improper procedure, and to also rule out the possibility of a defect in the meter itself, I compared results with another aquarist who has the same tester, and noticed the same degree of variances among the number of samples we did. Within the specifications of the tester itself, these test results do not indicate that the tester is performing outside its design limitations. And by the rule of thumb of 0.04 being the upper limit target for phosphates, these results would seem to indicate that "all is well." But if the goal is to keep phosphate levels under 0.04, then there seems like a fair amount of difference between a reading of 0.00 and 0.03. Or is it? I.e., are phosphate levels that tend to be "problematic" tend to be much higher, such as 0.10, 0.25, or higher? <Higher... something on the order of a half/0.50 ppm of free/soluble phosphate> One thing that I was hoping to achieve by testing for phosphate using a low-range sensitive handheld unit was to determine when it is time to change out phosphate absorption media. However if the variances between test samples can be as much as 0.03 (well, 0.04 actually) then one has to wait for a large jump in numbers before they can decide if they are seeing a trend, or just regular testing error/variances. Another reason for tracking phosphates would be for the diagnosis of a slow growth, or even tissue recession, in SPS. Ie., even if I don't see "nuisance algae" occurring in the tank (although that would be another reason to scrutinize phosphate levels). Since (I believe that) phosphate can interfere with the calcification process, I would still want to track phosphate levels as an regular ongoing activity - same as what one might do for watching nitrate levels, calcium levels, and alkalinity, just to be sure that I'm providing the best environment as possible. But again here is where I fall a little short in understanding of where "things are OK" turns into "things are not OK - look for a cause, and try to correct". Could a phosphate reading of 0.03 be too high for a SPS tank? <No... not practically> Thanks for your thoughts! -- Tony Slotboom <We really need to write/post descriptive pieces re these issues... Taken alone, phosphate is not a major issue in most all captive systems unless/until it reaches at least half a ppm... all else not being considered, or hopefully limited. As you so well state, other clues/observations re livestock health are far more valuable/useful here. The short of it here is that I would NOT be concerned if your soluble HPO4 readings were under 0.20 ppm. Bob Fenner>

Re: Mushroom Life Span--Turned into a Phosphate Question 10/1/07 Mich, <Andy> Sorry to pound you with emails, <No worries Andy> but I was hoping to update before you responded to my email below. <Ahh, appreciated!> So . .. odd . . . I bought a Salifert phosphate test kit today . . . which showed 0 phosphates in both my display water and my tap water. <Good.> Of course, the "place on the color chart and read from above" tests are also hard to read, but the water was clear--no hint of blue. <Good!> Is the Seachem test wrong/bad, or just hard to read?? <I would tend to trust the Salifert test kit over the Seachem. Mich> Andy

Salifert Phosphate Test Dry Regent Consistency 8/23/05 Hello WWM Crew, I recently purchased a Salifert Phosphate test kit from my LFS. The dry regent in it does not seem totally dry or at least it seems to clump together a little.  I am wondering if this is what you have experienced? Other dry Salifert regents have been bone dry as in the Ca test.  If your experience has found it to be sugar smooth I am going to take mine back.  I am concerned because my LFS's air conditioner has been out all summer and the store has had it's share of 90 degree days with 70% humidity.  I'm just wondering if the regent has been compromised.  Sorry to ask you guys but the Salifert website doesn't have any contact information. <Peter, the reagent should be free flowing as sugar.  I've used Salifert Phosphate Test Kits and the reagents were dry and not clogged as you say.  James (Salty Dog)> Thanks Peter Williams Tunicates/Sea Squirts and the Salifert Phosphate Test Kit Bob, Once again I need your knowledge regarding a couple of questions for my 100 gallon saltwater tank: (1) I noticed at my LFS that they had some of the large yellow and blue tunicates available (like the ones pictured in your excellent book, Conscientious.. p. 336). I am interested in adding these to my tank, but was not sure what their requirements are, i.e. light, current, compatibility, etc. My lighting is 4 x 96W 48 inch Power Compacts; two 10,000k super daylights and two 9600 actinics. These are on for 12 hr/10,000K and 14hr./Actinics. Fish are yellow tang, four cardinals, lawnmower goby, one damsel and one Pseudochromis. I also have several hard and soft corals, as well as two Tridacna derasa and one T. squamosa.  <Please see/read here: http://www.wetwebmedia.com/ascidians.htm> (2) Do you know of anyway to verify that the reagents in the Saliferts Phosphate test kit are still good?  <Yes... by making a solution of known or some given concentration having phosphates (you can even use a bit of "Coca Cola" tm for the phosphoric acid contained therein to give you a yes/no answer> I tested my tanks water and the reading was 0.0, but I also tested my tap water and my outside ponds water and these results were also around 0 ppm.  <They may actually be zero> This has me concerned that the test kit reagents are no longer viable. As I ordered it from my LFS, they did not know the age of the kit as they had none on their shelf and ordered this one for me. If you know of any solution that would act a good control or standard, please let me know. I would not be concerned about the phosphate level, but I have had some algae in the last 4 months grow on a couple of my live rocks and areas of the sand bed and I have to clean the green algae off the front glass twice a week (which the Tang loves to eat as I clean it off!). My protein skimmer, Aqua C 150, requires cleaning every 4 days. Nitrates when tested measure 0.0 ppm, pH is 8.3, and alk 3.43. I have a Korallin calcium reactor that now uses CaribSea ARM for the media and the effluent is alk 45 dKH/540 ppm CA; I was using SuperCalc Gold before switching to ARM two weeks ago, as I was concerned about phosphate from the Super Calc Gold might be the causing the algae growth. <Maybe> Thank you again for your advice in the past. Other then these two questions my tank has done very well, with water very clear and all life growing and active, due to the information you have supplied on your website. <Ahh, a pleasure to be of service. Bob Fenner> Regards, Kevin

RO I have high phosphate in my tap water--0.1ppm--so I bought a GE brand reverse osmosis unit. This RO water still contains about the same amount of phosphate, so I installed a Kent post DI canister. The water output after the DI still contains 0.1ppm of phosphate according to my test kit. Any thoughts? <although such water purifiers do not guarantee to remove all inorganic/organic phosphate... do consider that your colorimetric test kit is unable to read below .1ppm accurately. Such hobby grade kits really are poor quality. Still useful though. Have you tried to test the effluent of your RO (the reject water) to confirm that a higher level of phosphate exists there? It should... else more reason to suspect the test kit is inaccurate or unable to read. Do try other test kits for comparison. Kindly, Anthony>

Phosphate Test Hello, how are you <Just fine!> Could you tell me what company makes a good phosphate test kit? <The problem with all phosphate kits, as I understand it, is they all measure inorganic phosphate vs. organic phosphate. The major source of phosphate in our aquariums is inorganic, so most test kits miss a good deal of it. In general, I prefer Salifert's test kits. They are accurate and relatively inexpensive. LaMotte and Hach are supposed to be excellent, too.> (or even just a half way descent one). I don't think the one I have now is very good. Thanks, Kevin <You are welcome. -Steven Pro>

High phosphates not detected with old test kit Hi crew, I have been battling hair algae (Derbesia) in a 90 gal reef / 30 gal sump. I have been removing algae manually, reduced feedings, reduced light (650w total de HQI) to 8 hours per day. Top off water is from 100gpd 5 stage ro/di. I have read lots of books and this site extensively. I have been following suggestions from these sources without much progress. I had a small amount of razor Caulerpa in the sump and recently added a good size Chaetomorpha and red grape algae to the sump with ~65watts of compact fluorescent. Added SCWD on closed loop to increase circulation. Now for the question: I have been using Salifert test kits to test nitrate, nitrite, phosphates and alkalinity. The phosphate test did not change color so I assumed the phosphate levels were undetectable and not a problem. Today, I brought a .5 liter sample of my tank water and my top off water to the LFS and they were kind enough to test my water to help determine a cause for the algae. The LFS test showed phosphates off the scale! I definitely have high phosphate levels which helps explain the algae problem. When I got home, I tested the same tank water bottle with my Salifert PO4 test and it came back negative. Do the test kits expire? Should I throw out my test kit and replace it? <Hello Pat.  Usually the shelf life of the reagents in test kits are not to be trusted much over a year with an exemption to ph kits. If you have had it more than a year replace it and test again.  Salifert test kits are very accurate and reliable.> On the algae side of things, will my macro algae out-compete the hair algae and solve my problem naturally?<It can provided other measures are taken along with this.  Phosphate removers are like band aids.  If you do not get rid of the source of phosphates you will be continually using one of these products.  You didn't mention if you do a 10% weekly water change.  This is a must for starters.  You also didn't mention whether you are using a protein skimmer, this is a must to combat nuisance algae.> I added a poly filter as well.<The PolyFilter is a good idea, but is not designed solely around removing phosphates.> Do I need to add a phosphate sponge to accelerate the process? The LFS was recommending ROWAphos phosphate remover and a pressure canister. <I use a Magnum H.O.T. and run PhosGuard in it as a preventive measure.  As long as phosphate levels are low in the system, this will last quite some time.  Adding the macro is a good idea, it will compete for food with the nuisance algae.  I also have a Caulerpa growth in my tank. Many aquarists are going to refugiums with a live sand bottom with some live rock and Caulerpa and leaving the refugium lights on 24/7.  A lot of good has been reported as to the effect this has on minimizing nuisance algae.  Good luck.  James (Salty Dog)> Thanks for the info and the great books: conscientious marine aquarist, reef invertebrates, book of coral propagation, etc. -Pat

High phosphates not detected with old test kit James, Thanks for the reply.<You're welcome> I try to do weekly water changes. I have twin babies so I have been deficient in this area. I was doing 5 gal (5%) weekly. Have recently been doing 10% every 2 weeks. I'm trying to step it up a bit to 10% per week.  I have a Euroreef skimmer - ES 5-2. I am curious is this skimmer is too small. <I've looked on the net and the models I see start with a "6" number and they are rated for 100 gallons. I'm thinking you have an older model that is not listed anymore. If you still have the manual it should tell you what it is rated for.>  I have been looking at the Euroreef CS8-2 and the AquaC EV-180.  I'm not sure if it's worth $500 to upgrade a skimmer that works OK (not outstanding).<Keep in mind, skimmers need to be cleaned on a weekly basis> My tank is 48x18x24 with built in overflow. I have a 30 gal sump that has about 8 inch of water (~18 gal). I think my total water is about 100 gal. Should I upgrade my skimmer? <I would hold off and concentrate more on weekly water changes. You might want to try using Chemi-pure, a carbon based ion exchange media which does take out waste that a skimmer will not. I've been using this for quite some time with excellent results.> I suspect that the source of phosphate in my case is from over feeding. <Probably so, since I don't believe your tank is overstocked.> I was feeding once a day with flake: O.S.I. Marine flake and HBH Veggie flake 8. I was trying to feed very small amounts. But I suspect the main pump is blowing it behind rocks, etc.  <Your critters should clean that up. I would like to see a tank your size with about thirty hermits.> I am now adding Formula 1 and Formula 2 into the rotation along with Seaweed Select for my yellow tang and hippo tang. What the fish don't eat, the 2 cleaner shrimp seem to find.  I have cut back feeding to one cube of Formula 1 or Formula 2 every other day.  I'm still not sure how much/ how often to feed.  <A good rule of thumb is to put very small amounts in. When that is gone, add a little more up to a point where the fish lose interest in it. Don't worry about your hermits or shrimp, there will be plenty of food to dine on.> My livestock is: 1 yellow tang 3" 1 hippo tang 2" 1 clown 1 citron goby 1 yellow goby / 1 pistol shrimp pair 1 royal Gramma 4 blue green Chromis 2 cleaner shrimp asst. hermit crabs, snails One more piece of information: I bought this tank used in October 04.  The live rock had hair algae at the time I bought it. So I partly inherited the problem. Although the ongoing phosphates are probably from my husbandry practices.  <Sailfin Blennies (Lawnmower Blenny) are great at making algae disappear.> I'll check out the H.O.T. filter with Phosguard tomorrow - TGIF Saturday.  I'll discard the old Salifert test kit - it's definitely older than 1 year. The Salifert alkalinity test kit I have is also old. I have been dosing 70ml of B-Ionic and I cannot get dKH above 8 according to my test kit. But that's a different topic probably.   <Keep in mind 8 to 12 dKH is a good range. Too high of a dKH can cause the calcium to precipitate.> Thanks for the info. I will make some changes and start monitoring with some fresh test kits. I understand that the goal is to find the root cause and modify; not treat with Phosguard and macro algae.  Take care, Pat <Macros are a good natural way to help. Good luck, Pat. James (Salty Dog)>

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