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FAQs about Specific Gravity, Salinity 1

Related Articles: Specific Gravity, Salinity, Product Review Marineland Labs/Aquarium Systems Hydrometer, Part 1 By Steven Pro, Choosing Synthetic/Natural Seawater, Major/Minor Seawater Constituents, Frequent Partial Water Changes

Related FAQs: Spg 2, Treating Tapwater For Marine Aquarium Use, Seawater, Seawater 2, Seawater 3, Seawater 4, Seawater 5, Seawater 6, Reverse Osmosis Filtration, Test GearUsing Hyposalinity to Treat Parasitic Disease,

Salt concentrations in ppt (parts per thousand) and ppm (part per million) to percentage readings http://edis.ifas.ufl.edu/VM007 http://www.koiclubsandiego.org/SUBcategory.php?categoryKey=3&subCategoryKey=19&subCategoryName= Salinity&PHPSESSID=f7a64e77d6b7b88b6b21f06b6b31ffb3  

Salt concentration links as requested   2/2/06 Hi again, Thanks for your quick response to my questions. I found these two sites helpful in determining salt concentrations. They both relate ppt (parts per thousand) and ppm (part per million) to percentage readings. The first of these is very reputable and most helpful, and deals most directly with my original question about ich and salt concentrations. The second deals with koi pond chemistry but was helpful nonetheless. http://edis.ifas.ufl.edu/VM007 http://www.koiclubsandiego.org/SUBcategory.php?categoryKey=3&subCategoryKey=19&subCategoryName=Salinity&PHPSESSID=f7a64e77d6b7b88b6b21f06b6b31ffb3 Thanks again Phil <Ah, thank you for this. Will post/share. Bob Fenner>

Refractometers 2/14/04 Quick question regarding refractometer.  Love this site!   <thanks kindly> I have a plastic hydrometer, which from reading on this site is not the best of readers, nor was I aware of the cleaning.   <correct... they are not that reliable or durable. A quality glass hydrometer is actually the best all around. Do keep both and compare the glass as needed> Which I am doing now....  I work in a lab, we have a refractometer which is checked daily with two controls.  One is DI water, reading should be 1.000 +/- 0.2, the other is 8% NaCl with a reading of 1.032 +/- 0.3.  The controls are at room temp.  I see calibration is mentioned, and I note on the refractometer that is calibrated every 6 months.  Now can I use this for my salinity checks?   <certainly> I brought a sample in before and it was quite a bit lower than my reading with the plastic one. <not surprising... some of those plastic hydrometers are easily corrupted (dried minerals from poor cleaning, dropping/jarring... and QC> This refractometer is a Reichert TS meter. If I bring in a sample from home, the temp on that sample is quite lower than my tank ... my tank is at 78. Will this make a difference in reading?   <the diff is small but please do simply heat the sample up. Use a water bath to float your sample in (its container/baggie) to warm up> This is a lab refractometer (I work Hemo and Chemistry) we use this refractometer for urines, though usually this is only used after a problem with our automated instrument.  So can I use this, does the temp make a difference.   <yes... but there are published scales for compensation... mere fractions of a difference though> When I do any testing on my aged salt mix (to replace weekly changes) I always have the temp matching the tank. <very important...yes> Thanks so much Kris <best regards, Anthony>

Back To Normal (Returning Fish To Normal Specific Gravity) Hi all, <Hey there! Scott F. with you today!> I was wondering if I needed to slowly raise the salinity ~5ppt a day from 14ppt back to 35ppt to return fish back to my main system after a month in hyposaline conditions. Or, can I safely do a drip acclimation that spans that range in salinity? It seems that water changes with NSW conditions would be safer but the drip would be easier, please advise. Thanks, Ryan   <I'd be more comfortable with the gradual increase to 35ppt. The drip method can work, but it might be a better idea to do it the slow way...HTH! Regards, Scott F.>

Hydrometer Recommendation Hi All, <howdy> I am looking for a recommendation for a Hydrometer / Refractometer for measuring specific gravity.   <your best bet/value IMO... a glass hydrometer (do spend the extra and get one of the $20-30 units). These are arguably more reliable then even the handheld refractometers> I have the usual cheap one, but am told I should get a better one for hypo salinity treatments in QT tanks, etc.  If you have a link of one or can comment on the refractometers on marine depot (around $70), I would greatly appreciate it. Thanks, Andy <the cheap hobby grade handheld refractometers are good... but not as great as one sometimes here's about. Reliability in refractometers is to be found in table mount models (not influenced easily by temp) and on lab grade equipment. Refractometers that are made cheaply overseas (imported $15-25 and retailing $50-80) are not always as good as you might hope for them to be. Whichever you choose... simply avoid using the plastic hydrometers as a primary. Anthony>

Hydrometer Recommendation 2/3/04 Thanks, do you have a link where I can find an acceptable glass one (perhaps a brand name)?  I checked marine depot and a couple other places online and can only find the cheap hobby ones.   <no easy link here I can think of. I have used the high end hobby ones like Marine Enterprises brand with satisfaction FWIW. Anthony>

Thank God for your service (salinity rise) 1/20/03 I was wondering..... I had a spike in my salinity, for about a week, I was away and did not perform proper maintenance.  My salinity spiked to 1.027 in my reef and fish tank.  I was keeping it around 1.02 - 1.022 <I suspect that the drop back to 1.020-1.022 was more harmful than the "spike".  While you were away, the SG slowly rose due to evaporation.  When you lowered it, I suspect you did so fairly quickly.  Also, Natural Sea water is 1.025, and lower SG is more stressful on  corals than higher SG.  I always recommend 1.025 for a reef tank.> It seems that my Wes. Brain coral lost about a dime amount of tissue. Do you think it will grow back, hoping that is does not get a infection?  Thanks!<Probably not an infection, just a reaction to the stress of the salinity changes.  The tissue may take a very long time to recover or may be permanent, but the coral should be fine.  Also, just for accuracy sake, All corals known as Wellsophyllia and Trachyphyllia are all now considered Trachyphyllia.  HTH.  Adam>

Too Salty (12/28/2003) Hello everyone I have a 90 reef running for 4 years now and for some reason my salinity is running high 1.028 how do I go about lowering that to 1.026 without affecting my ph, alk.? I just ordered a refractometer should be here Monday otherwise have been using the old plastic style, I know Egads those dreaded plastic testers. I have been reading through the sight and have not seen a ? regarding high salinity and how to lower safely. I do water changes aerated with RODI water as I also do with top off water that is buffered to 8.3 for ph, like wise when I add my salt I have been backing off on salinity mixture but this has not lowered the salinity of the tank water and have been doing this for some time. if you need more info I'll be glad to let you know, your help is grateful Brian <Those plastic swing-arm hydrometers are notoriously inaccurate. I love my refractometer--great investment. Before changing anything, I'd suggest you use this to measure the SG of your tank and your replacement water. Of course you're topping off (replacing evaporated water) with buffered RODI water with no added salt, right? If you kept the salinity of your replacement water at 1.023 - 1.024 and do small water changes 1-2 times per week, your tank salinity should drop gradually. I like to keep my tank at 1.024. Others prefer a bit lower or higher. Hope this helps. Do keep us posted. Steve Allen>

How Do I Use This Thing?  Float Hydrometer Primer >Hi, I'm setting up a 110g saltwater tank. >>Cool. >I was given a glass Saltwater Hydrometer (by Marine Enterprises), approx 12 inches in height. The problem is: I have no idea how to use it. No instructions were given with it. >>No problem.  They don't come with instructions for the most part.  It's a float hydrometer, and it's really easy to use. >Is there a website with step by step instructions on how to use the meter properly. This meter has what looks like little pellet balls and some type of wax in the bottom of it.   Thanks for your response, America >>Easy-peasy, America, no website needed.  What you will need is something to put some of the water you wish to measure the salinity of into that is TALL enough to let the hydrometer float freely.  My favorite is a device I make myself out of clear plastic tubing (you can get this at the fish shop) that is capped and sealed on one end (needs to be watertight).  About 1" in diameter is fine.  Then, you fill it with the water, drop in the hydrometer, and you want to look at the lines on the really skinny part.  There will be one fat one that's pure water, a salinity or specific gravity of 1.000 - that's pure water.  (Btw, don't measure especially cold or warm water, make sure it's room or tank temperature - between 73F-82F - as this WILL affect the proper measurement).  So, the hydrometer should float so that the lines BELOW this 1.000 mark are what hit the top of the water - this measurement is your specific gravity. It is at this point that I MUST urge you to start buying books, because (and please don't take this as an insult, we all start from a position of no knowledge), if you don't know how to use the simplest hydrometer made, then I fear there is much other invaluable information you don't have as well.  There are MANY excellent beginner books, Bob Fenner's "The Conscientious Marine Aquarist" is one, and you may wish to search for books by Martin Moe, Jr., C.W. Emmens.. aw heck, to http://www.reefs.org/library/reading/  and http://www.reefs.org/library/reading/beginner/beginner.html and search the database for books on saltwater for beginners.  Also, you will find (if you have regular internet access) that the talk forums for our site and reefs.org are EXCELLENT for quick information.  Our sister site is http://www.wetwebfotos.com/talk - know that many of the folks who answer questions here are "on duty" there.  If you do join, let 'em know that Seamaiden/Sea Maiden sent ya.  ;)  All my best, and Happy Holidays.  Marina

Hydrometer trouble - 12/18/03 Hi crew, I've been visiting and reading the FAQ everyday for a year now and you have helped me many times. <great to hear> Thanks for all your hard work it is truly appreciated. <tanks a million, bud>  A couple of quick questions, yesterday I decided to do some maintenance on my sump/fuge which is a 30 gal that feeds my 55 gal reef.  My SG has always been 1.024 using a floating glass hydrometer. <very well> I replaced most of the sumps 30 gal with premixed saltwater, problem is after completing the water change I broke my glass hydrometer. <DOH!> I went to the LFS and bought the plastic "box" version, did a read, 1.030 (as you always say YIKES!). <Don't trust it> I want to start replacing 2 gallons per day with freshwater to get SG back to 1.025 area. <Woah!!! Get a second or third opinion. Try either another glass hydrometer or if you know someone with a refractometer>  I understand that consistency is more important than accuracy, however should I trust the "box" or get a new glass hydrometer for calibration purposes? <New glass and another opinion>  I don't want to over react based on a possible faulty reading from the "box". <agreed!!> Also if the 1.030 is accurate, based on 85 gal total water volume, minus 100# LR, do you think 2 gallons per day a reasonable starting point for moving SG .001 per day? <That should be about right you could do a little more>  I've read of similar events in the FAQ's, just looking for a "mental" calibration. <get a second or third opinion if possible> As always thank you for your kind response. <My pleasure. ~Paul> Mike

Salinity and health - 12/16/03 Hi,  As I've been reading on in various books, articles, ETC. I've read that the ocean has a salinity of close to 35 ppm (sp. gr. 1.026) however the LFS (and any hydrometers I've seen) suggest that 29 ppm (1.021) is perfectly fine. <Some even state 1.018-1.019. Interferes with pathogenic abilities to thrive and survive. I don't recommend this though except in quarantine. I personally keep salinity at 1.025 in my main tanks> This got me really confused, as I would love to see these animals thriving in the best possible conditions for them, should I begin raising my salinity or is 29ppm good? <How are the animals doing?? If it isn't broken then it doesn't need fixing??>  I have a fairly lightly stocked 125 gallon A small school of Chromis, Firefish goby, cinnamon clown, yellow tang, six-line wrasse, sebae anemone, colt coral a few cleaner shrimp, and an emerald crab. Any advice would be most appreciated. <I would work towards 1.025 if there are problems or if it will ease your conscience but otherwise use your inhabitants as your barometer for change. If it ain't broke then don't fix it. ~Paul>                                                                     -JIM

Specific Gravity Specifics! Hi Scott <Hi there!> My salt water aquarium has been running now for a week now since setup. I mentioned to you that I am trying to sort my heat issues out and in the last week my tank has been running close to 80 deg Fahrenheit. <Not too bad...> What I need to know is does the temperature affect the salinity reading? <It can> I hope this is not the case as I have my salinity measuring 1.022 which is perfect right? <Ya' know what? I used to be a believer in lower specific gravities for a lot of reasons, but after much experimenting, I've concluded that natural ocean specific gravity (generally 1.024-1.026) is the way to go...I shoot for 1.025> I should have the fans in soon and also gonna be doing one or two mod.s to the hood of my tank so I can get more air to circulate. <Excellent! That can make a difference in the heat buildup...> Thanks Again Regards, Ziad Limbada <My pleasure! Stay cool! Scott F>

Hypo-salinity and Hydrometer Accuracy Hello Bob, Steven, Jason, and the rest of the crew, This is my first question for you so I want to say that your site is wonderful and has provided me with a wealth of information, which has allowed me to be much more successful at this hobby than I could have ever thought.  Without this site, I would likely be one of those in and out reefers who drops the hobby after a year, now I'm hooked for life.  I'll keep this short, no story behind why I'm asking.  I am having a problem with hypo-salinity treatment.  I believe that my hydrometer readings are off.  I have three: a Deep Six, a Sea Test box-style, and a floating glass (with a built in thermometer and made for aquarium, rather than lab use).  All three read differently!  So I chose to trust the floater because I have read the others can drift over time and both are not brand new.  I have conversion charts galore, but they are worthless if you don't know the calibration temp of the hydrometer or if the hydrometer is not accurate anymore.  I believe I am failing to maintain a proper 1.009-1.010 SG and that my true SG is more like 1.012-1.013 (this would be true if the floater were calibrated at 60F).  After three weeks in hypo and several FWD's my fish are still showing spots and scratching a bit. >>Do know that there are documented subspecies of Cryptocaryon irritans that do quite well in low salinity environments. >Questions:  Is there any way that I can mix a test sample of water with a controlled amount of salt (I have Instant Ocean brand) at a specific temperature in order to test the accuracy of each hydrometer?   >>Yes.  I would first calibrate with distilled water. >Is there any other way for me to be sure that I am at the proper SG level?   >>Yes!  Invest in a good quality refractometer! >Even if I am now at 1.013, is it possible for the ich to be so virulent as to survive that, and continue to re-infect my fish?   >>Yes.  This would necessitate the utilization of copper or formalin treatments. >Can the spots I see be bacterial infection from the parasites bursting out during FWD's? >>Yes, but not so likely as to keep the same appearance of the ich (at least not in my own experience, secondary bacterial infections really LOOK like infections). >With sincere gratitude, Manny >>Do a search on Terry Bartelme, he's written quite a bit on ich, treatments, prevention, etc.  Then, I would search the reefs.org library, as well as Advanced Aquarist for the same.  I've only recently learned of the ich subspecies, both instances mentioned by folks working in Hawai'i.  Hope this helps!  Marina

- Specific Gravity & Temperature - Hi, Hope all is doing well there.  I have a 75 gallon F/O tank.  My fish are:  2 percula clowns, 2 lemon butterflies and 1 coral beauty angel. Please tell me what you recommend for tank temperature and specific gravity.  I have been keeping the tank at 76 degrees and the specific gravity at 1.021.  Thank you, James <James, I'd shoot for 1.025 for salinity - it's what the ocean is typically at. As for temperature, you could go a little higher, but there's nothing wrong with 76F - 76-78F is ideal. Cheers, J -- >

Saltwater too Salty - 8/28/03 Dear WWM Crewperson: I just made 32 gallons of saltwater for my storage batch, and I made it a bit strong, around 1.030.  I would rather not dump some out and add fresh water.  Can I add some of my top-off water to my water change bucket at the time of a 2-4 gallon change in order to bring it down to 1.025?  Thanks, Rich <Yes you can. Should be no problem. Bob Fenner>

- Conductivity & Salinity - Quick question: I have recently acquired a Milwaukee conductivity monitor. I want to use this to monitor the salinity of my tanks, but I cannot find a table for converting conductivity to salinity at a given temperature. I have looked all over the Internet. Any idea where I can find a table or graph? <Well... my only tool available here was the Net, so I used Google to find this: http://www.radiometer-analytical.com/all_resource_centre.asp?code=112&s=go I think you might find the information you need there, but you should also contact Milwaukee Instruments.> Thanks, Steve. <Cheers, J -- >

Hydrometers Hi Bob, <Hello Tyler> I have read your articles regarding the care of one's salinity and I agree that testing in a separate container helps prevent breakage; however, I recently bought a new glass hydrometer made by Living Sea, and it is labeled "Marine Enterprises SALTWATER HYDROMETER/THERMOMETER specific gravity 75?F".  The problem that I have is that the chart that I have for converting specific gravity to salinity was designed for an instrument calibrated to read 0 in freshwater at 60?F---I'm presuming that the instrument I now have is set to read 0 in freshwater at 75?F---how might I compensate for this dichotomy (or where might I find a conversion chart for 75?F hydrometers)?  Or does the difference in index temperatures matter at all? <Does matter, or should I state "it can". Likely at the tank temperature you're going to be at this device will register a couple of thousands (0.002) low on actual specific gravity. You could do an actual check (with water of calibrated temperature and raising it to tank temperature) to see what the difference actually is. I would do this and make the mental adjustment (that is, that a measure of 1.025 is likely to read about 1.027). The usual note here: More important than the actual specific gravity is its constancy and even more important the composition of the media...> Thanks for your advice, Tyler Reynolds <Welcome. Bob Fenner>

Re: Hydrometers So the difference will be arithmetic, not geometric or parabolic? Or is it simply too similar to warrant distinction within the boundaries of 1.020 and 1.025? <The latter. The relationship is not arithmetic, but differential, however "close enough" w/in the "nuts and bolts" of actual aquarium practices to be so here. Bob Fenner> Thanks, Tyler

Measuring Salinity... the long way around the barn 6/23/03 I have a TDS meter and I was wondering if its reading could be used as a measure of salinity which could be converted to specific gravity. <really not necessary/ideal> I got a link to an interesting site in the forums, but I can't get a good correlation between what my tank reads on the TDS meter and its specific gravity. I was hoping you could enlighten me. <use you instruments instructions or a good conversion web site to work in reverse. A good average for seawater is 32ppm (about 1.024 SG)> My understanding is that a TDS meter basically measures the conductivity of water (so many miliSiemens/cm) and then transforms that reading to parts per million. <yes... but it can be influenced by other solids/additives you put in the water> Conductivity is related to the solids dissolved and should increase as salinity increases. Can such a TDS ppm reading be converted to salinity? <you are an engineer aren't you <G>?> If it does, what is the salinity or TDS reading that corresponds to say 1.025 specific gravity at 80 C? <your father was an engineer> TDS meters are fairly inexpensive nowadays. <ahhh... a glass hydrometer (not plastic!) is more reliable, does not need calibrated... and costs about $6> It seems they are fairly accurate and it would be nice if they could be used for more than gauging the health of the RO membrane in an RO system. <OK... but over thought/unnecessary IMO> Thanks for your help. Henry <best regards, Anthony> Emergency In The Reef Tank... Hello,  And thanks for taking my question. <That's why we're here! Scott F. at the helm tonight> A few days ago, after doing my normal weekly 10% water change I had a problem with salinity (.030) in my reef aquarium due to a faulty Hydrometer. <Yikes...been there before!> My salinity is now down to .023, where it should be? <Personally, I shoot for 1.025, but 1.021- 1.026 is acceptable> But my tank has taken a turn for the worse. I had to replace about 7 gallons of saltwater with fresh over 3 days. My water is now very cloudy and my fish appear to be struggling for oxygen. My PH level is low (7.6) but I'm using additives daily to correct that. Will this cloudiness eventually go away? Or did I replace too much water for my bio filter to handle? <Depends on the size of your tank...If you did damage your biofilter, you would want to avoid and more large water changes for a while, unless ammonia and/or nitrite levels are registering> Will I lose any livestock through this process? <Well, it depends on the levels of ammonia and nitrite, if present. Just take careful corrective actions as needed...nothing too radical. You could utilize chemical filtration media, such as activated carbon and/or PolyFilter, both of which excel at removing organics and potentially toxic substances from the water> Do you recommend using bacteria (Nitromax, cycle) in my case? <Well, if you're getting ammonia readings- it couldn't hurt to "re-energize" your system with some additional bacteria...Be decisive, but be level-headed, when taking corrective measures...Hopefully, things will work out okay with your tank! Good luck! Scott F> Charles Tizano

Salinity and New Aquarium Grateful to have found your site.  Every LFS tells me something different. Say the water temperature is 80 degrees (it sometimes gets to 103 in the summer here, and no a/c)<103 F is pretty darn high,>, and the hydrometer is calibrated for 75 degrees, what adjustment would I have to make to figure out the correct salinity of the water.<Published charts of the temp correction of salinity over a wide range reveal very little appreciable change. Not even noticeable between 75 and 82 F on a plastic hydrometer. should be fine, (thanks ANTHONY C> Also, I'm trying to set up my tank per Michael Paletta's book "The New Marine Aquarium".  In it, he mentions that if you use a protein skimmer you need to add a supplement to the water to replace any nutrients that might get skimmed out.  Can you recommend a good supplement? < http://www.wetwebmedia.com/suppleme.htm> <do check out the FAQ's also> I'm setting up a 29 gallon FOWLR tank with an Emperor 280 Bio Wheel, 1 300gph power head, thermometer, and AquaC Remora skimmer (returned the Seaclone per the numerous posts on your site).<agreed>  I want to add some shrimps, snails, crabs, a goby, a royal gamma and 2 perc clowns.  Is that the order that I should put them in? <should be alright>  Also, is a 29g too small for a brittle star? <Please read over the Seastar materials stored on the WetWebMedia site, Keep reading my friend and good luck on your new Aquarium, IanB> Thank goodness for WetWebMedia!

Reef specific gravity 1. What should the salinity be for my reef tank. I have a 55 gallon with 75 lbs of Fiji rock and live sand. I have a few soft and hard corals, a few anemones and many different invertebrates. <I keep my reef tank's specific gravity as close to 1.025 as possible. Make sure the water temperature is correct for your hydrometer as temperature affects the reading. You can find this answer and many others by reading the articles here http://www.wetwebmedia.com/marine/index.htm and beyond. Hope this helps Don>

Refractometer Problems Hi guys, just picked up one of these units... <Phil here wishing he had a refractometer.> the unit says it is calibrated to 0 when shipped, I used a couple of drops of bottled spring water and got a SG reading of 1.004, then with tap, same reading, then with tap I boiled for a few minutes, same reading, then tested tank water 1.027, tested tank water with old hydrometer 1.022, should I think of the refractometer as accurate (not against the hydrometer as I know the refractometer is more accurate, but wondering why the reading of SG with the plain water used), or should I adjust that 1.004 reading down to 0 and then consider my tank readings to then be accurate, I already adjusted it down to 0 and now am getting a tank water reading of about 1.024.....Thanks again... <Hmmm... I would check with the maker of the unit.  It could be that the refractometer was damaged in transit to your home.  But if I was in your shoes I would just adjust the reading as you have done.  Hope this helps!  Phil, who is going to check his SG using the "plastic box"... LOL>

Refractometer Problems Try testing your refractometer with RO or distilled water. "Spring" water comes from the ground and has mineral content read by the refractometer.  Same with tap and boiled water would/should actually be a bit higher still as the actual water evaporates from boiling.  Try it with pure water. 

Hydrometer Hi guys, looking forward to the new book, it will hit Canada I hope?..... <indeed... we have several distributors of it waiting for it in CANADA <G>> I have a question, I use an old "deep 6" swing arm hydrometer, I always mix my salt so that it is the same SG as my tank (.024),now I know about these being calibrated at a temp of 75f,my FOWLR tank is always at 80-82f.....am I still at .024?,any idea what I am really at?, does it matter as long as consistent?.....Thanks again.... <mostly the latter (consistency). Published charts of the temp correction of salinity over a wide range reveal very little appreciable change. Not even noticeable between 75 and 80 F on a plastic hydrometer. No worries. Anthony>

WWM AWOL? - hi guys, sent this email a few days ago, didn't get any message back, actually haven't gotten any response from my last few q's I've sent over the last while, you guys must be busy, I'll try this one again...thanks..... <Seems unusual, we have quite a few people working on this and try to make sure no one slips through the cracks. My apologies.> Hi guys, looking forward to the new book, it will hit Canada I hope?..... <I believe so... if I recall correctly, we've already been contacted by a distributor in Canada, so it should work it's way to your LFS.> I have a question, I use an old "deep 6" swing arm hydrometer, I always mix my salt so that it is the same SG as my tank (.024), now I know about these being calibrated at a temp of 75f, my FOWLR tank is always at 80-82f.....am I still at .024?,any idea what I am really at? <Nope, no clue - swing arm hydrometers are typically consistent measures, but not necessarily accurate measures. And I doubt seriously that any of them are calibrated in the true sense - the swing arm pops out of a machine and is tested against a standard, perhaps weight - but the process of manufacture is such that a dozen of them will read 12 different numbers. To truly calibrate, you need to compare against something like a refractometer, which will give you a ballpark - plus or minus - and more accurate readings.> ,does it matter as long as consistent? <Yes and no... some hydrometers are way off... imagine if at 1.024, you've actually been over 1.030... is good to check. See if you can track down someone at an LFS or local club who has a refractometer.> Thanks again. <Cheers, J -- >

Lowering temperature and proper salinity - 3/25/03 What would be your best suggestion to lower my temp to 78 degrees? <I would just lower it by moving the dial on the thermal regulator of your heater> I realize this must be done slowly, but how slowly? <By dialing it to 78 on the heater I think the heat will dissipate slow enough. We are not talking a radical change from 80 to 78 in my opinion> Could I float a couple of frozen milk jugs up top every day until it lowers to 78? <No need to> Thank you for the advice and for the suggestion to look up Ron Toonen -- I plan to read up on him. <Cool. Great guy. You will find him to be very thorough and a great asset to the marine hobby>  In your opinion though, what would the ideal salinity level be for my tank? <35ppt I knew you were going to ask that question. See here: http://www.wetwebmedia.com/spg_salinity.htm and here: http://www.wetwebmedia.com/spgfaqs.htm It is important to note a few things, one being that the hydrometer measures salt/mineral density in a given water sample. It then can be used to estimate the salinity level based on that. Another thing to note is that most areas (not all but 98% of ocean environment maintain a salinity of 35ppt So it is ideal to keep it in that range. I use a calibrated refractometer to measure my pre-made salt water and measure at the temperature of my reef tank. In any case, if you are using a hydrometer, I recommend a quality $20-$50 range glass floater type and aim for about 1.025> I currently keep it at 1.021.  Is this too low? <I think so. Slowly add and be sure not to go up more than .001 per day.>  If so, could I just increase it gradually through my weekly water changes? <Yes>  I do a 10% water change every week. <Very good>  Thanks again for your help.  You guys are life savers! <Nah....your the life saver we're just the life saver supporters. Paulo> :)

Blue Damsels salt levels I currently have a 29 gal. Brackish tank, I have been told that blue damsels can live with a salt level of 1.017 my tank is currently 1.018 with 2 archers an Orange Chromide and some bumble bee gobies. I wanted to add a few damsels but am kind of afraid to add fish that I thought needed 1.020 at least. Can they tolerate brackish water? Thanks <They can tolerate the lower salinity but are much better off being kept at true marine levels. There are a few species of Damsels that are from fresh or brackish areas, you might want to check into these. Take a look at http://home.rochester.rr.com/akom/FAQ7.htm for a list of the freshwater ones and do some research for the brackish varieties. Ronni>

- Semi-Auto Top off - Jason, <Good evening...> I've reviewed as much info as I could find on your site regarding auto top offs and my primary concern is the failure of a valve or switch. <I think perhaps I wasn't entirely clear - I was trying to convince you into a different 'way' to change the water; not in small, constant amounts, but in one fell-swoop - more akin to using buckets, but also incorporating your desire to use these tanks. I do not propose you go full-blown auto top-off, but rather crank the valves by hand.> How reliable are the Kent float valves. <They work.> What's the most reliable switch? I like the simplicity of a float valve but it would be difficult to build in redundancy as one could by using multiple switches. <Again... these items add unnecessary complication - consider just putting a hand valve where you might use a float switch.> Regards, George <Cheers, J -- >

Spg Hey crew!  I have been reading quite a bit on here lately and have come to the point where I would like a little bit more in-depth explanation of some of the topics available. <Okay> 1) I have read the Specific Gravity and Salinity articles several times ( http://www.wetwebmedia.com/spg_salinity.htm).  It points out pretty reassuringly that floating hydrometers are perfectly acceptable for the average hobbyist and that specific gravity stability is more important than a specific number. (a 1.020-1.025sg range is considered fine). <Yes... precision is often more important than absolute accuracy here>   However, when going through the FAQ's I noticed one in which Bob stated that we shouldn't really shoot for anything other than 1.025sg (give or take .001). <Also a "truism"... especially for the majority of in- or non-vertebrates kept by aquarists>   I am just wondering how close I need to worry about this.  I currently have my tanks at 1.025, but want to know if there is any importance between the two differing ideas. <Mmm, some. If really concerned I would opt for a more accurate "checker" like a better grade glass hydrometer, or a refractometer...> 2)  I also read about the dangers of acclimating a saltwater fish too quickly to a higher specific gravity.  While challenging their systems to maintain a " salt and solute" balance, are there any long term effects known other than this immediate stress? <Some longer term ionic imbalance problems and their consequent manifestations. Bob Fenner> Sincerely, Ryan A.

Refractometer 3/3/03 Thanks for the quick and thoughtful response.   <always welcome my friend> It is a hobby grade item (considerably less quality there than I had anticipated!)   <unfortunate...yes> By glass hydrometer are you referring to the glass thermometer-looking devices that float in the water (the higher they float, the denser the water?) <correct> PS  I read about an IMAC being held in Chicago in May.  Are any of y'all going?   <I have declined to visit/speak there. Bob has declined for his own reasons too.> Are they worth attending? <almost certainly... networking with fellow aquarists, enjoying the speakers, gleaning info and chatting with all. Surely an education to be had. Please also consider MACNA. More info at www.lmas.org > tom <kind regards, Anthony>

Store owner looking to measure saltiness I own a local pond retail store and I need a tool to accurately measure salt in my koi pond do you sell this tool? <Mmm, no. We don't actually sell anything but the books we produce, but you can likely buy a refractometer (most accurate, precise tool... from most any wholesaler that carries marine gear or etailers. A bunch are listed here: http://www.wetwebmedia.com/marlinks.htm Bob Fenner>

Refractometer 2/28/03 I recently purchased a refractometer designed for salinity measurement.  After calibration, I noticed that it was way off from what I thought I had in my tank.  Using a plastic SG meter, I measured 1.024; with the refractometer, it was 1.029.  I keep the plastic device clean and free of build-up, particularly on the pointer.   <very good... and for all of the daily FAQ readers: it is a necessary habit to give your plastic/glass hydrometer a rinse with distilled or deionized water after every use to prevent mineral build-ups that will skew readings in time> With another, brand new plastic meter (from another company), I also get 1.024.  I read up on refractometry, especially regarding its use in determining the SG of urine.   <I hope there isn't a seawater v. urine analogy coming <G>> In that context, I read that the accuracy can be affected by protein.   <dammit... ;) > Reasoning that even with a good skimmer there is dissolved protein in the tank water, I thought that this might account for the discrepancy.   <ahhh...no> After all, a display tank will have more dissolved in it than just sodium chloride.   <the amount of proteins/incidentals in urine is... ahhh... very different from habitable seawater. (Although I have seen some aquariums in my travels that were so neglected that it looked like the fish were swimming in piss). Refractometers are used everyday in seawater by science and aquarists alike in the tens of thousands of unit numbers. The problem with your refractometer is either simply that it is a defective unit... or, more likely, that it is a hobby grade unit or a handheld unit. Handhelds are slightly effected (more so) by temperature than table tops (although the difference would not be so great to explain the .005 dif you noticed). Furthermore... those $50-100 hobby models are dubious if not junk too often. For that kind of money, you could get 2 or 3 top shelf glass hydrometers that are much more accurate and never need calibrated.> I would be curious about your experiences with refractometry to determine SG/salinity. thanks tom <if you do have a lab grade or table top refractometer, then I am honestly at a loss to explain the discrepancy short of defect. Refractometers are nifty toys... but really not necessary. Use your plastic hydrometer for convenience and safety (no matter how many times I call them junk <G>) and have a decent $20-50  professional glass hydrometer on hand to spot check the plastics periodically with. Best regards, Anthony> Specific Gravity - 2/17/03 Hey Guys- Got a question about maintaining specific gravity...I premix my RO water and heat it and circulate it and use it to top off and do my regular water changes...but what formula do I use to take into account for the increase in salinity due to evaporation? Thanks <Evaporation and water changes are two different things, of course. There is no formula. You need to add fresh water daily to your marine tank to maintain the normal and original salinity on set-up. Your weekly/monthly water changes are then simply adjusted to match that salinity. I'd advise using a glass hydrometer to compliment your plastic one (unreliable). Anthony>

- Evaporation - WHICH WILL EVAPORATE FIRST SALT WATER OR PLAIN WATER? ALSO WHERE CAN I GET SOME INFO ON THIS SUBJECT? THANK YOU <I'm trying very hard to recall my chemistry classes from college - I do believe saltwater and freshwater will evaporate at the same speed, or something very close to the same speed - if you recall, ocean water is only 1.025 times more dense than regular water so... it's going to be a small difference if any at all. I would try entering the phrase "evaporation rate" into your favorite search engine on the web for starters, then perhaps a trip to the library. Cheers, J -- >

Mixing Salt - 2/13/03 Hi guys, Have a quick question about mixing salt. It's been a year since I had my take up and going, but now I'm close to starting again.  I had been using Coral Life salt, but have switched to Tropic Marine Salt.  Question is this....The Coral Life always had a little sheet that described approx. how much salt to add to so many gallons at a set temp.   <Temp has no measurable effect within safe tropical temperatures on your hobby hydrometer... no worries here at 76-80F> The box of Tropic Marin has nothing.   <Excellent salt! The best IMO> So....Is there a set guideline to how much salt I should be adding to my water to get a SG at 1.023 to 1.025. and at what temp. Thanks Bryan <Easy my friend... they are all very similar. Its about 1/2 cup sea salt per gallon of water. Anthony>

- Determining Specific Gravity According to Temperature - Hey what's up? <Hey.> Quick question, I have this temp conversion chart but I'm not sure how to read it. For example if I have a measured specific gravity of 1.0265 at 82 degrees with a hydrometer that is calibrated at 77 degrees then what is my true specific gravity according to this chart? <Well, start with your measured temperature and SPG. Then move horizontally to your calibrated temperature; this should give a reading of 1.0271. That is the adjusted reading.> Thx for your help. Angelo <Cheers, J -- >

Salinity & Temperature Dear Bob: <Connie> I was at a meeting of SeaBAY last night (in SF area) and learned that the salinity in my LRFO tank should be at .025, also that the temperature for my tropical fish should be 80 degrees.  Do you agree?, <Mmm, most systems will do best at near seawater conditions. About 1.025 for specific gravity... and 80 F. is about right for many tropicals... but there are arguments for keeping most cooler, some warmer. You can read about these on WetWebMedia.com> My salinity is now about .022 - over what period of time should I raise it to .025, if this is correct?? <No more than 0.001 per day.> Thank you Bob. <Welcome. Bob Fenner> Connie C.

Plastic vs. glass hydrometer Anthony, Again, I can't tell thank you enough for you advice.   <truly a pleasure> I thought I'd share with you some news today.  You mentioned in my original question that there must be a simple answer...I think you're correct.  On a whim, I took a sample of tank water to work with me (I'm a veterinarian), and checked the salinity.  My refractometer read 1.017!! I couldn't believe it.  My hydrometer at home is telling me 1.024.   <heehee... piece of crap plastic hydrometers... I don't know why they even make them. Don't get me wrong... the cheap glass hydrometers can be equally inaccurate... but they don't stray. They are consistent and can be trusted after a single comparison to a reference point like a refractometer for those that cannot afford one. Plastic hydrometers can be corrupted in so many ways- junk.> I was so dumbstruck, I checked it twice more on separate refractometer.  One read 1.016 one read 1.017. >Please tell me this is the likely cause of my problems.   <hard to say... but very stressful indeed. And the difference in success between species was the difference in tolerances perhaps> If this is it...I'm not sure whether to laugh or cry.  I have closed off my top off, and assume that it is best to allow natural evaporation to gradually return the salinity back to normal. <its not that scary low that you need to add salt. I'll agree> Jeff <best regards, Anthony>

Raising salinity Just Live Rock I only have live rock in my tank at the moment and my spg is 1.020. If I want to bring it up, should I still do it slowly or can I boost it in one shot since there is no livestock, per se, in the tank yet? <Actually... there's a bunch of salinity-sensitive life that is the "live" part of your rock at risk from such quick changes. Do elevate the spg at most about 0.0005 a day... by removing some existing water, adding some of higher density in its place. Bob Fenner>

Plastic Hydrometers Hi there, Currently, I'm having two brands of hydrometer. One is from aquarium systems and the other one is from marine enterprise inc. They're both giving me different set of readings. Which one should I trust ? What would be the effects be (inhabitants consist of fishes and corals) if the SG level is high (let's say it's above 1.026). Thanks. <Plastic hydrometers are known for this. I would use the one that reads zero with RO water.  Some people average between the two. As long as the new water matches the old water and the SG is between 1.023 and 1.028 (a bit high) you're alright.  Craig>

Overcrowded  Hi once again <Hi Bryan> I have a 55 gallon bow front with a magnum 350. My pets are a 10" snowflake moray, 3" crown squirrelfish, 3" red emperor snapper, 6" lionfish, and my personal favorite, a 7-8" panther grouper. Yes, I know it is crowded! Yes, I Know it will get worse! <Ah yes, I remember!> While I am deciding which of my pets to sell back to the pet store I have a couple of ?'s.  <Shoot> My fish guy is telling me that I should have my tank at 80 deg and 1.019 salinity. According to everything I have read on your site it should be 1.023-1.025. He also says that the correct salinity depends on the temperature of the water. Is he wrong or am I missing something? <He is half right/ half wrong. Yes, SG depends on temp to a degree. No, at 80 F SG should be 1.023-1.025 as per most salt manufacturers labeling. Most affordable plastic SG "gauges" are temperature corrected for water heated to approx. 76-80F. Spectranometers and soluble salt meters must factor in temp for the most accurate results.>  My second question is what should I expect from a pet store? Is it fair to ask them to hold a fish for a few days with a deposit? Is that a standard practice or should I just give up on trying to get them to do this? <Each store has it's own policy. The better ones will hold a fish for even a couple of weeks with a deposit. Find a store that provides you with the service you need to acquire and keep healthy pets.>  The main problem we have had is that most of the fish we have bought there have died within 3 days even though we have followed all of their instructions. Now, do I get another pet store or what? <I would rely on the outcome of your experience, and either keep it or change it based on your experience. Trust your feelings. How do you feel? I try to avoid stores with high mortality problems. I am attracted to stores where the stock is healthy and has a good survival rate and where I get accurate advice not necessarily aimed at generating sales.>  Thank you for all the help over the last couple of days. P.S.  The deaths weren't due to overcrowding as we only had three small fish then. <You are more than welcome Bryan, please don't hesitate to write WWM. Do make good use of a quarantine tank and reduce your overcrowding and you are on your way to a lot of enjoyment! Best Wishes, Craig>

Coral health in high salinity Hello Anthony, Pete from Western Australia again. <cheers, mate... its very good to hear from you! My apologies for the delay in response, I was out of town giving a presentation to the Los Angeles aquarium society. A great club and time was had> A query regarding the adaptability of corals to water with higher than usual salt levels.  <hmmm... interesting> Shark Bay is an area with limited flushing, high evaporation and low rainfall, and as such salt levels in some places are up to nearly twice normal seawater!  <Yikes!> At our location the SG is around 1.029 rather than the usual 1.026.  <no worries here> There are some nice corals around us here, probably at salinities of 1.030 or more. Can most corals usually cope with such salt levels, or would the specimens in these areas have developed a tolerance over many generations? <some tolerance... but also some concern here for the long term viability of trying to run that in a captive system. In the ocean, at least many/most other parameters are more in line... crashing waves, high dissolved oxygen, unlimited food and dilution of waste products, temperature stability etc. The reality in your closed system will be different despite your best efforts. Higher DOC levels, lower dissolved oxygen, less temp stability, etc. To add a salinity on the highest end of the threshold to that may be too much for many coral species. I'm worried that it will be a problem. Do ameliorate/dilute the display if possible (unless this is an open system?)> With regards to our 600,000L display tank, we are pretty much stuck with the 1.029 SG because of the size of the tank and the limited available freshwater. If this salinity is a concern, the obvious solution is to collect corals (we have permission for this) from areas with similar salinity.  <yes... perhaps best at least to begin with I'm sure> However, having dived these areas frequently and seen consistently high concentrations of zooplankton, I suspect that many of the corals from this region are heterotrophic. The difficulty in feeding corals in a tank as large as ours has me leaning towards aposymbiotic species, especially as the water may be clouded during feeding of heterotrophs, which is not a good thing for a public display... it would be too hard to explain to most people - they just want to see pretty fish in clear water.  <hmmm... do you have the terms confused my friend? Aposymbiotic creatures require frequent and heavy feedings (as in "not symbiotic" and must feed). Heterotrophic means the same thing. Hermatypic corals are the photosynthetic reef builders that I think you seek. Arghh... the science of it all <smile>!> Perhaps we could identify and collect species which are known to be mostly aposymbiotic from these areas, or perhaps we could feed more heterotrophic species after closing and let the foam fractionator clear the water overnight... <I would avoid most or all heavy feeders for the big displays. Better for small displays that you can feed heavily and afford to do larger and more frequent water changes on> The alternative is to collect from deeper, "cleaner" waters just outside of the bay. Visibility here is often over twenty meters (mmm...20m+ vis...:)  <just beautiful! I hope to see it one day> so I suppose corals would be mostly aposymbiotic. We could use an underwater light meter to match the light conditions between the point of collection and the position in the tank (wouldn't it be nice if this information was given with all collected corals...).  <yes!!! very wise... please do this for all, my friend> However, this area has SG around 1.026. How would these corals take the transfer to SG 1.029?  <on the point of a .003 change... no trouble at all, I suspect> What duration of acclimation would be appropriate? <short would be fine in fact. Hours no doubt> As always, I value your input and thank you for your time. <it is my great pleasure to share my opinions and experience. I wish you the very best and look forward to hearing from you again. Pictures too when you can!> Regards... Pete McKenzie <kindly, Anthony>

Re: Bio Balls/PH (hydrometer, water quality) <<Hi > The tank is a reef tank, 75 gallons, two refugiums, and 80-90 lbs live rock. My nitrates according to my test kit are 0. I test my top off water and buffer to 8.3. I also test the salt mix and buffer to 8.3 if needed for water changes, yet it still drops off to 8.0 every morning. Even after 20% water changes the ph still is around 8.0 before the lights come on the next day. I feed moderately once a day with either flakes (formula 1 and 2) or a 1/2" x 1/2" cube of frozen food I made from Sanjay's recipe. I have just recently developed a slight Cyano problem in one small area of my tank. I also purchased a Tropic Marine hydrometer and found my salinity to be 1.028 and slowly lowered it to 1.025. My plastic hydrometer was way off matched against the TM hydrometer and another plastic hydrometer. My alk is in the 4.12 range every morning and jumps to 4.65 after adding b-ionic, yet will be a little above 4 the next morning. Does anything stand out that I am doing wrong? Would Kalk be the answer or would I be better off adding commercial buffers to bring the ph up? I am worrying about nothing? <<Yep, totally normal to have depressed pH in the AM before lights. Test at night before they go off to feel better. Using alk is normal, especially with calcium lovers and higher calcium levels. Not to worry as long as you keep it in the range it's in now. You can dose Kalk at night and it does stabilize pH. Use carefully according to directions, drip very slowly and test pH (not a problem with that, hey?) Sounds like you are doing just fine! No worries, Craig>>

Lowest salinity safe for crab and shrimp? Hello again. I apologize for so many questions, there is so much to learn. I have read over all the FAQ's regarding lowering specific gravity for reduction of ich. I am leaving my tank for 2 months without fish hosts to greatly reduce parasites. <After two months, there will be no more parasites. They will all perish in one month.> There is a Lysmata cleaner shrimp and a white spotted hermit crab in there with live rock, my question is what is the absolute lowest I can reduce salinity to without killing my crustaceans? <No need to do the low salinity with no fishes, but anyhow, I would not go below 1.018.> Right now I have it at 1.019 with a temperature 84. <I would leave as is.> Regarding my 2 quarantine tanks one with a maroon clown and neon goby and one with purple tang and neon goby what is the lowest salinity possible these fish will tolerate? <I have read of treatments as low as 1.010.> If my maroon clown shows no signs of parasites and seems very healthy can I please take out the CopperSafe, it has only been in for 7 days, but she has been visibly parasite free for 6 days. <I would run the suggested course of treatment.> I know she is sensitive to copper and I want to take it out as soon as is safe to do so and put in a piece of live rock to hopefully help with reestablishing bacteria after the copper. <There are other treatment options in you do not like copper; daily water changes and freshwater dips are my two favorites.> Also is it okay to take copper out of purple tang's tank after 2 weeks even if she still has faded spots/scars on her body. <Same advise as above> Thanks again for all the wonderful help and advice, I would be so lost without your website. No one at any of my LFS can ever agree or seem sufficiently knowledgeable to trust. ~Kylee Peterson <That is a shame. -Steven Pro>

Hydrometer? Hello Bob, I'm starting a new saltwater aquarium and looking for a good and reliable hydrometer. Would you please recommend one? Thank you very much. <Please read here: http://www.wetwebmedia.com/spg_salinity.htm and the FAQs linked on top. Bob Fenner> Sincerely, Dung

Salinity <<Greetings, Tyler...>> I have a 30 gallon saltwater tank and I was wondering what would be the best and safest way to lower my salinity. Thanks <<Add conditioned freshwater in small amounts until you've reached the salinity you desire. Ideally, you don't want to move more than one thousandth per day - that's the last number in the SG: 1.02x  Cheers, J -- >>

Salinity Fluctuations? II Hey, who said I had a plastic one? <Almost everyone does.> Ok ok you caught me. That is what Tim at Elmer's said was best. Guess I be jetting out today to get a glass one if Seahorse or PetSmart sells them and then it is live rock for sure. <Glad to hear it.> Going to get some locally as the link that Steven sent me regarding the message boards and some of those peoples not so fun times with ordering rock online. In the end it will be worth the extra money. <To many it is.> Thanks all for ALL your help it is a wonderful site and you are truly wonderful people willing to share your expertise and experience. Colleen, Pittsburgh <Hopefully, we will get to see you later at a PMASI meeting. -Steven Pro>

Salinity Rob, Still a bit confused, one final question/thing about salinity. My reading indicates that when threatened with disease, ich, etc. it is SOP to lower rather than raise salinity level and increase temp ????? <Yes, in general. But it is also standard operating procedure to maintain most all organisms at/near normal conditions to reduce stress. Bob Fenner>

High specific gravity Good morning, My problem is that in my 80 gal. reef, the specific gravity has gotten up to 1.026. My feelings tell me that this is a little too high.  <not really unnatural for many reef animals, but indeed high for aquarium husbandry. Things run smoother a lower down on SG in aquaria> I've been adding RO top-off water but that hasn't seemed to have any effect.  <that sounds unusual... and I hope the RO water isn't raw (you need to aerate it and buffer it for 12 hrs before such use)> Should I change out maybe 10 gal. of water and just add that RO water back into the tank without any salt in it to try and lower the specific grav. I'm kind of at a my wit's end . <its really not that big of a deal and doesn't stray fast either. Keep a closer eye on it in the future to prevent it. In the meantime. Test your math for the water change first on a smaller scale (10 gall of 80 gall with fresh) by mixing 7 cups of tank water with one cup of fresh water and then test the SG. If so... fine but go slow. Good and bad things should happen slow in a well planned tank. Kindly, Anthony><<Mmm, have to take out some of the solute-laden water and replace with less solute-laden... to reduce Spg. RMF>>

Salinity for Reef Tanks In Alf Jacob Nilsen books he said to keep salinity at 34 parts per thousand .Some protein skimmer makers say keep it at 31 parts per thousand what is the best salinity for reef tanks. And if it is to high how should it be done lowered  -R. Gibson. <Most reef keepers are aiming for a specific gravity of 1.023-1.025, which corresponds to about 31-34 ppt. If you wish to lower, slowly add extra freshwater. Change no more than 1 ppt per day for extra caution. -Steven Pro>

Gills Swollen on Green Chromis I notice the other day that my Green Chromis seems to have swollen gills. The gills seem red and irritated, however the fish still eats but not as active. I check my salinity and it was 1.028(to high) so now I slowly lowering it to 1.024. Would this cause the Green Chromis have the above symptoms? Would it be wise to place him into the hospital tank for a while? I want to get more fish and place them into the hospital tank but I am not to sure if I am dealing with a parasite or a disease. My other fish have not been effected by this. Thanks <swollen gills are not a conspicuous symptom of a given disease and may have been aggravated by the high salinity, although a true 1.028 should have been tolerable for a short period if elevated slowly (as I suspect it occurred from neglected evap top off). Observe for up to three days more... the condition stabilizes or improves... ride it out without medications (only if necessary). Else... QT for sure. Anthony Calfo>

Hydrometer accuracy? Okay. I have heard that the floating hydrometer that I have (Marine Enterprises about 13" long, calibrated at 75 degrees), although supposedly a very good one, may not be accurate. I also wanted to be able to test from my tank a little easier. So, I went out and got a SeaTest Hydrometer by Aquarium Systems. It immediately jumped to 1.0295!!!! My floater always reads 1.024-1.025. And, yes, I did knock the bubbles off of the SeaTest float prior to reading the results. Which one is correct? <Very likely the floating unit is closer to what is real> What should I rely on? <Please read here: http://www.wetwebmedia.com/spg_salinity.htm> My calcium test is not working as advertised and I am wondering if the salinity might be a problem. Carbonate hardness looks okay at 110. Linda Swenberg <Good lessons to be learned here re accuracy, precision, the "nature" of tests, testing. Bob Fenner>

Specific Gravity Hello Mr. Fenner; <You actually reached Steven Pro. Anthony Calfo and I are helping out for the time being.> I have a silly question, and hope this is not a bother. <An unasked, unanswered question is silly.> I am a fairly new to the salt water trade, (6 months). I have read through the FAQ's on the WetWeb and could not find the answer. I also have read through your book. Both talk about raising and lowering SG, but does not tell exactly how to complete this task. My box Hydrometer broke, I bought a new one. I believe it is the six inch Hydrometer, suppose to keep your hands dry, any way I tested my SG this weekend and it was at 1.019. I need to raise the SG back up to 1.023 to 1.024. Can you please tell me how to accomplish this? Thank you for your time. Both your site and book has helped me immensely. <The easiest way to accomplish this is over the course of several water changes. Mix up some water to approximately 1.025 and do several small (~10%) water changes over the course of a week or longer. -Steven Pro> Sincerely, Lori

Low Salinity Stress? Hello Mr. Fenner, <Anthony Calfo here...fellow Pittsburgher, and happy Steeler fan today!!!> I am new to the hobby and have about 6 months of experience in saltwater and my 55 gallon tank is also approximately 6 months old. I have read the WetWebMedia boards in search of something related to this, but I could not find anything that I thought could help me. I had a problem a month and a half ago with a Yellow Tang who developed, or was infected with parasites when I got him. I gave him a freshwater dip and quarantined him for approximately 3 weeks and he seemed to be doing good in the qt tank. One morning I woke up and turned on the light and he was dead. Anyhow, the store I bought him from had me do all the tests on my main tank where he originally was, and all the readings were ok. They said to drop the salinity 2 pts per day until I reached 1.10 s.g..  <Severe. Only acceptable in systems without invertebrates/live rock and dubiously extreme. Just because some fish are strong enough to survive it doesn't make it right. This methodology has sprouted from an anecdotal article which included the support of a the old Pittsburgh AquaZoo curator who does consult a local store. Very controversial.> They also said to hold it there for a month to make sure that if there were parasites in the tank, they would not survive. < conditionally, but not guaranteed> Anyways, I did that and the fish looked great, but the live rock looked like it was dying and all of the worms were gone. <not a surprise...obviously and visibly damaging to everything but the fish> At the end of the 1 month period, I started on Wednesday slowly increasing the salinity by 2 pts per day. Everything looked ok except now my Coral Beauty seems to be refusing to eat, but my False Percula Clown is still chowing like a pig. The Coral Beauty will not eat flake, freeze dried brine, Pygmy angel frozen food, of Sea Veggies. When the clown starts to feed he swims around with him but will not eat anything. I do not know if my rock is dead or dying and it is causing ammonia to rise and that is affecting the Coral Beauty or what.  <surely damaged your biological filter...to what degree remains to be seen> I am also confused on why my levels are what they are. Could you please try to help me out and tell what I should do. <at this point patience, resumption of normal routine and water changes> Some of the live rock has turned white during the drop in salinity. I thought that the algae dying on the rock could also have led to the Coral Beauty to stop feeding, because he grazed on it a good bit. <a small stress... the salinity was principal and more severe> I don't know if I should pull the rock, or it will come back on its own as the local fish store says.  I would sincerely appreciate your professional opinion on this matter. Thank You, Jim. Pittsburgh, Pa <it will come back on its own. After the water chemistry is assuredly stable, add some fresh live rock to inoculate the damaged rock and all will be OK in time. Best Regards, Anthony Calfo>

Hydrometer (addition of salt to koi pond) I need your help in testing how much salt I need to add to my pond. I have done a partial water change and I need to know how much salt I can add. I bought a "SeaTest Hydrometer" and I need to know if is possible to test *my Koi pond water with this. If so, what should the reading be on the meter for a pond with plants. Thanks for your help. <Mmm, not really useful/practical to use a hydrometer for salt additions to ponds... the small amounts of salts in such applications are not easily, precisely, accurately measured by such a tool. The long and short of what I sense you want to know is "just how much" salt to add... as in per the volume of your system, end results of the addition. I would guesstimate how big (gallons... as in about 7.5 gallons per cubic foot... or by filling with a watch... and figuring how many gallons per minute in filling a "pickle bucket" of determinate volume), and add (incrementally, over a period of days), about a pound per one hundred gallons.  Much more to say/state... if you were interested in "how much" real salt you have already, and to augment you might look into a conductivity meter (rather than density measure with a hydrometer) or other "marine aquarium" salts measuring gear... Do take care in how much, how soon you add salt to your system... as the rapid die off of algae, sometimes beneficial nitrifiers, increased osmotic pressure... can be too stressful to your livestock (fishes, invertebrates and plants)...  And more to the point (at least mine) is "what do you hope to accomplish" by salt addition? If any of this is incomplete, not clear to you, let's keep discussing ahead of application. Bob Fenner>

Re: New tank setting it up Well, Bob I put in dechlorinated tap water in my 55 gal. tank and let it stand for a day or two. I mixed in a 50 gal. bag of Instant Ocean into the tank with 2 powerheads and a Millennium 3000 filter running. After 24 hrs, I put some of the water in my SeaTest hydrometer and the needle went all the way up to 1.030!!?? Is this normal? Should I add more fresh water? <Normal, yes... there really isn't 50 gallons of water in your 55... not just due to displacement... do the math... Length times width times height in inches divided by about 231 cubic inches per gallon... So yes, remove a proportion of the current volume and replace with just freshwater> I also have a CPR Bak Pak2 skimmer which I have not installed yet, should I put it in already? <Please read: http://www.wetwebmedia.com/marineSetUp.htm> Thanks for taking the time to answer my questions Bob. I know that you are a busy man and you do not have to do this so thanks again. <No worries, be chatting. Bob Fenner>

Refractometer I have a Refractometer and a Hydrometer (deep six) which do you consider a better choice? <Mmm, better choice?... Well, the refractometer is decidedly a "better choice" for accuracy and precision of measure of actual salinity... And the hydrometer is the "better choice" for ease of use (though not as accurate or precise) in measuring density/specific gravity. I would likely use the latter for most daily, occasional use.> I used 5% NaCl solution to calibrate the refractometer and my salinity of my tank, which read 1.023 with the Hydrometer, read 1.017. I cannot convince myself which is better. <Mmmm, you may be becoming "too involved" here (like myself, we would likely lose on Jeopardy (tm) due to too much considering, thinking about the "real" answers... when a simple, general sense of what is involved is all that is necessary). Please read here: http://www.wetwebmedia.com/spg_salinity.htm and the FAQs beyond. Be chatting, Bob Fenner> Alex

Issues For Discussion Dear Robert, <Howdy> Hello there, it's me again!!! I have a few questions to ask you, so please bear with me. <Okay> Michael and I are at odds as to what the comfortable salinity should be regarding my reef tank. He thinks that I should bring it down all the way to 1.017-1.019. The SCMAS group convinced me to bring the salinity up to 1.024 and up. Will you kindly help settle this question?!? Do I have it up too high and SCMAS is wrong or is Michael's assessment too low?!? Whatever you say, I shall adjust accordingly. Every time he comes to clean my fish tanks, he drastically brings it down by adding too much fresh water and brings the salinity down somewhere between 1.019-1.021 which kills a fish or invertebrate (or so I think). What to do?!? <By and large almost all captive marine systems should be kept near seawater spg... 1.025 or so... There are many valid reasons for keeping spg artificially low for periods of time... to save money on salt mix, reduce parasite pathogenicity, allow for greater oxygen solubility... But permanently leaving spg low has proven to be trouble... especially for non-fish livestock as you mention. I would elevate, leave yours in the 1.024, 1.025 range. Bob Fenner> Sincerely yours,  Aleida Ann Graichen

Re: Hi Bob (hydrometers) thanks for getting back to me so fast Bob, maybe you could give a seminar in prompt response to some of my coworkers... <Mmm, doubtful... all I know is a bit about ornamental aquatics> I'll still be returning the hydrometer, it gave me an spg of 1.029 on the made up water, added 1/2 a gallon of freshwater (cold, no going through any metal pipes/hot water heater here), waited till it was the same temperature... and it came back as 1.030 spg. I got all the bubbles off the arm both times, so I know it wasn't that. C'est la vie. <This actually is NOT much variance... once, a group of us at one of our old stores got out a dozen "cheapy" glass hydrometers and tested them... the "range" of readings spanned eight thousandths in the same tank! Bob Fenner> hope you have a nice weekend, and thanks again! Mike Harmful SG Change? Hi Bob, I have a 29 gallon reef with 55 lbs of Fiji reef live rock and 20 lbs of live sand. The tank has an Eheim 2213, CPR BakPak 2R, ZooMed PowerSweep 228, and AquaClear 201 running on it. I have a Mandarin, Watchman's Goby, Pistol Shrimp, Feather Dusters, Green Star Polyps, Bubble Coral, and Yellow Scroll Corals in there now. Soon to arrive will be 4 Banggai/Banner Cardinals, 4 Peppermint Shrimp, and 4 Camel Shrimp. <Mmm, sounds like a nice set-up... but I would not place any but one of the cardinals and a couple of the shrimp in this size system> So my question is: how big of a specific gravity change is harmful/deadly to inverts like shrimps? Let's say... in a 12 or 24 hour time period. <In good shape, about 0.001, one thousandth a unit (g/cm3) can be tolerated in the upper teens to near seawater (1.025) range in a day or so... Please read: http://www.wetwebmedia.com/spgfaqs.htm> I've been bad, and my SG has ranged from 1.020 to 1.024. I'm trying to get into the habit of 1.025 from now on. Nothing has died yet, however; usually, the swings occur when I add DI fresh water to top off once or twice a week.  <If there is this much evaporation, I would mark the water level on the tank and top off daily> The instructions for my DI unit said this was okay, and the SG would remain stable. However, I guess this is not true, and now I am premixing all water that goes into the tank. <Good idea> Secondly, would Feather Dusters do better in a bright, high flow area, or better anchored on the bottom in a slower flowing "cave"-type area with live rock overhanging?  <Depends on the species. Many are virtually dredged up from mucky under-the-dock areas... Other species are collected in clean, shallow reef areas. See our site (www.WetWebMedia.com) re these worms> I'm reading Tullock's book (But we carry yours at the store I work at, too! Do you have a suggested retail price for your book?) and he has a section on Worm Rock. <Mmm, maybe M/TFH have suggested retails... In the years of working with Microcosm we purposely set the suggested price points low and narrow at all levels of distribution to make our printed works affordable and re-sellable by independents ("Mom and Pop" stores). Think folks are still selling the paper-bound for about thirty US and the hardbound for ten, fifteen dollars more. Bob Fenner> Thanks, Ben

Salinity What should I have the salinity at for a 150g fish tank with clown trigger, emperor angel, Naso tang, yellow tang, and lunare wrasse. I was wondering because my salinity is at about 1.020 and the trigger and emperor angel are twitching and scratching-but I don't see any ick! The tank is a year and a half old and all the levels are in check. Thanks in advance, Kevin Ballard <Please read this part and the following FAQs on this subject: http://wetwebmedia.com/spg_salinity.htm Bob Fenner>

Q-Tank Mr. Fenner, Just a couple of questions concerning quarantine and spg level? My tanks spg is at 1.023, I am going to put my emperor angel into my quarantine tank ASAP. Should I bring down the spg level to 1.017 in my quarantine tank or would lowering to much right away kill my angel? <Hmm, should be okay to lower... if this animal is in good health now, of sufficient size (four or more inches)... better to not make "this jump" all at once... but about a thousandth of a point per day. Please read over the Quarantine and Spg sections on the Marine Index of the www.WetWebMedia.com site and accompanying FAQs for much more. Bob Fenner> Thanks, Ron

Trusting Hydrometer Hello- First off thanks for your devotion to this hobby.  <To hobbyists and the planet> I recently moved and had to make the change from well water to city water. Upon setting up the tank (75 g. with sump, skimmer etc.) I had major problems. Lost all shrimp, inverts etc. the first two days. All that is left is a green Chromis and a Sailfin tang. At first I thought the problem was lack of dissolved oxygen from disturbing the DSB, (and maybe part of it was) but after reading your articles and FAQ's I was concerned about my salinity, it seemed as though I was adding more salt to my water than I normally did to get my "bobber" hydrometer to read 1.023. I went out and bought a new Hydrometer swing arm). To my horror it registered off the chart, above 1.030. <Yikes> I felt/feel horrible. I exchanged a few gallons of water for fresh water, but I don't know what the s.g is at or how much to change it a day, I know you say not more than .001/24 hr, but this is hard if I am off the scale. <Still, better to do gradually at this point...> I am having trouble believing my instruments, this is a bad feeling. Should I invest in "refractometric means" of measuring salinity. Sorry this is so long, please advise. <The refractometer is a nice tool to have/use, and valuable for research, having lots invested... but a decent "regular" calibrated hydrometer (and/or one to check it against that you can trust) should yield sufficiently accurate and precise measures. Sorry to read of your losses. Bob Fenner> Thanks, John Gray

Raising Salinity??? Hello again Mr. Fenner, I recently emailed you about copepods & offered to buy you "little brown bottles" @ the SuperZoo-What a great show that was. <Agreed> I got tired of asking everybody @ the show if their name was Bob Fenner. Maybe your next book should have a picture so all of us can put a face to the name. <Hmm, not that attractive. Should have sent you to: http://wetwebmedia.com/BobFBio.htm > Anyway, my 50g tank has been w/out habitants for 2.5 week now w/ the temp @ 81 & salinity @ 12. My quarantine tank is aprox. the same. My question is: when do I start raising the salinity & to what level is optimum.  <In another two weeks... a thousandth per day... to 1.025> The two fish in the q/tank are a 3" red sea Sailfin tang & a 2" flame angel. I am considering adding gobies, hawks, Firefish, cleaner shrimp & getting the 50g tank ready for reef.  <It likely goes w/o stating that you will be waiting a few weeks plus after returning the existing stock...> I will be adding a 180g 3 sided room dividing tank after the hot Las Vegas summer is over. I have seen flames & sf tangs in reef tanks before & wonder if they will eat soft corals or sponges if I add them to the 50. Is it worth a try? <Yes, worth trying... the Flame may nibble... more so in a 50 than a 180... but likely no big deal> And will it do any harm if they do eat them? <No> Thanx again for such a great website & sharing you expertise w/all of us! Also, (last question) What is your opinion of the "eco-system" set-up & their "garlic" product for ich? <The Eco System looks like a nice product (no first-hand experience), but very pricey... Garlic, have heard folks say it does some good in some cases... am not convinced it is a panacea. Bob Fenner> Craig

Re: Raising Salinity??? Mr. Fenner, You look a lot younger than the mental picture I had of you.  <Ha! Images can indeed be deceiving... I always thought women had a staple in their belly-buttons from perusing girlie mag.s as a youth! Carved in stone back then> I read your bio & now I value your opinions even more, quite impressive resume and it sounds like you really do enjoy life to the fullest.  <Hmm, guess this is where I should chirp in, "Don't believe everything you read" or such...> Especially the Sushi part. If you are ever in Las Vegas, I know a few great sushi spots & would be happy to treat you. <I've heard there are some good ones out your way> Now my questions. A week from today my main tank will be 4 weeks w/out habitants and ready to start raising salinity, then adding my quarantined fish (Red Sea Sailfin & flame angel). My tank has grown algae to the length of an inch or so on the rear glass, along w/the copepods mentioned before.  <Great> When I put the 2 fish back in the main tank, will they proceed to eat the algae & copepods? <Some of both yes> Should I clean some of it off? Or should I leave it be & not feed the fish for awhile.  <The latter> Will they overstuff themselves & throw all of my (perfect) water levels off? <Very likely not> Also, If I add a orange spot goby or similar bottom dweller to my quarantine tank for 2 wks. min), will I have to add some sand to the small tank? <A good idea> Thanx again in advance! Craig <You're welcome my friend. Be chatting. Bob Fenner>

Salinity and sponge questions... Robert, I have a couple of things to ask. First, I must say I am fairly new at reefkeeping. I have a 55 gal tank with a variety of soft corals, a sponge, gorgonians, an anemone, a few SPS corals, three fish including a Percula clownfish, Lawnmower Blenny, and a Coral Beauty. I have various inverts such as cleaner shrimp, turbo snails, blue legged hermits. I have live rock also. I keep the water at a fairly constant 78 degrees. (I know that temperature is hotly debated also.) I am trying to be rather thorough because of my next question: What is the proper salinity for this tank? <About NSW, near seawater, 1.025... and more or less steady...> I have read many different guides giving me everything from 1.021 to 1.026. I have read at the higher levels that fish may become stressed. I have also read that the higher levels are better for coral. <Both so> My salinity is currently at 1.024-5 the variance is due to evaporation. I have always found your advice to be indispensable, I cannot seem to find what would be appropriate. Also, if my current levels are off, over what amount of time do I change it? Your help is greatly appreciated. <No worries... and do take a look at the spg/Specific Gravity section including the FAQs stored on our site: www.WetWebMedia.com> My second question: I have a red tree sponge I received from a friend, it is fairly large (8 inches), and has five or so branches. I have been feeding Dt's phytoplankton 3 times a week and an invertebrate supplement. After 3 months of seemingly good health and color, the sponge is losing color and becoming a little clear on one of it's tips. I have it away from the other animals/corals in the tank and it has not been exposed to air in my care. I have read the WetWebMedia FAQ and anything else I can find on the care of these sponges. My calcium is 450 ppm, ammonia, nitrates and nitrates are nearly zero. Lighting is two 96 watt power compacts. My phosphates are .003ppm (Probably due to the invert food you think?) <Maybe, but/and this is low/enough...> My question is what could be the culprit and what if anything can I do?  <Something's (plural) missing in your system. Do try other foodstuffs, blended fine, blasted via a baster in this colony's direction two, three times a week, with your filter pumps cycled off (best with timers) for about fifteen minutes... add a vitamin and iodide supplement to this blend ahead of serving> Should I attempt to cut away the necrotic tissue, and how? <Unless "it's" very "bad" I wouldn't... can be easily excised with a sharp single edge razor blade (underwater and watch your fingers!)> Sorry for the long winded questions, I just want to give you all the info that I thought might be pertinent. Thanks, Brandt <I understand. No worries my friend. Bob Fenner>

Re: I always seem to come back to you! :) Raise temp to about 82f, and drop spg to about 1.017 - SLOWLY. You mustn't drop the salinity too fast, for the sake of your hermit crab, and other tiny crustaceans you certainly have hiding from your Labroides (cleaner). Don't drop that spg more than 2-3 points over a 24 hour period, same thing for bringing it back up when you decide the ordeal is over. HOWEVER - that wrasse will potentially/likely keep ich under control quite nicely. The thing with ich is, once it's in a tank - it's there FOREVER, unless you leave the tank fallow (no fish) for at least 6 weeks, or strip it all down, throw away the rock and substrate, bleach the tank and other hardware, and start over. Nobody wants to do that. Adjust the temp and spg, don't feed the wrasse his favorite food, maybe buy a cleaner shrimp to help the wrasse, and get a quarantine setup before you buy any more fish! Best regards, and good luck, -Lorenzo p.s. There is a 'support our site' somewhere within WWM... I don't do the maintenance there, so I'm not sure where it is... but it lets you donate (NOT tax-deductible) directly. But don't tell Bob I 'solicited' you or anything... !

SG Variations Hi Bob! I was hoping you could help me crack a mystery this time. <Let me put on my Sherlock hat...> On one of the newsgroups I'm on, someone posted that when they test the SG in their tank, it is lower than the SG they get if they test the water in the sump. Thinking this to be impossible based on the amount of circulation, I advised that he take identical containers, and the same volume of water in each, one from the tank and one from the sump, because perhaps it was an optical anomaly from reading his glass float-type hydrometer from different angles. I also advised that if the readings were still different, to let both containers sit out for several hours so temperature would be equal, then see if there was a slight temperature variation causing the different readings. He still had the same variance--which was .002! <Very unusual> I thought, there is no way this could be the case--everyone knows the water in the sump is the same as the tank. So I tried it--my tank was at 1.024 and the sump 1.025. I was using a Coralife Deep-Six. I had to return my refractometer for a replacement last week, but I'll test it again when the new one gets here--although someone else also did the test with a refractometer on their tank, and got variance as well. <Bizarre> Have you ever experienced this, and if so, what causes the variance? It seems impossible, but everyone that has tried it so far has found a variance (ranging from 0.0006 to 0.002). <Perhaps some accumulation of more dense organics at the surface water of such sumps> Although this is not an urgent matter, it is really bugging me because I can't think of any reason for these readings to vary. Also, a quick update--all seems well with the new system. I moved everything yesterday. So far, the move doesn't seem to have caused a cycle. I'm still testing for ammonia and nitrite daily. I did wash the sand that came out of the old tank (with system water from the old tank) before adding it to the new tank. : ) I'm glad I did--there was lots of nasty stuff in it. Is that normal to have lots of detritus and other matter built up in the sand bed, or was my sand bed perhaps not deep enough to effectively process the waste? <A bit of both> The purple tang is still the same--but I'll give it time. I didn't try to treat the Lymphocystis in any way. The three tangs are hiding a lot right now and haven't yet figured out where the algae clip is, but they all come out for flake and frozen brine. I couldn't bring myself to trade in the Archaster typicus stars at the LFS--I figured I bought them, they're mine, and I'll deal with them and see how the sand bed looks after a few months. Hope your weekend was well. Chat soon. --James D, Perplexed Aquarist <Equally perplexed, but non-plussed Bob Fenner>

S.G. check Hi Bob, Just a very quick, simple question. What s.g. do you recommend ??? <Near seawater conditions... about 1.025... and steady... I use and urge others to pre-mix, store new synthetic (if they use same)> Fish are emperor and queen angel, clown and Picasso trigger, regal and yellow tang, maroon clown and Foxface, and red sea 4 line cleaner wrasse. (Some are in the process of being moved :-), new tank etc ..... ). <Ahh> It is at about 1.024 at the moment ....... my hydrometer needs cleaning, so it could be 1.025 .... but the last time I checked it with a clean hydrometer, it was 1.024. Do you think this is about right ??? <yes> If I were to "sway" it in favor of any particular fish, I would say in favor of the emperor angel ..... but obviously not at the cost of others :-) <I understand, and agree. Bob Fenner.> Cheers, Matt

Water Density Measurements... First off I just want to say what a great book Conscientious Marine Aquarist is. It has been invaluable to me and its the first book I recommend to anyone who's asked me about getting into this hobby. I have a question about reading my hydrometer. I feel kind of silly, but none of the tables I've seen for temperature adjustments have made sense to me. I have a hydrometer which is calibrated at 78F. For my water at 82F, it gives a reading of 1.024. What is the true specific gravity/salinity of my water? And more importantly, how do I adjust the reading for those 4 degrees? Thanks a lot. >> Hmm, the "true" specific gravity? In all likelihood it is very near the 1.024 value that your hydrometer is calibrated to... and I wouldn't obsess about the absolute spg at any length... there are a couple of variables, artifacts if you will, that influence hydrometers readings on the basis of temperature... (compression and gas solubility issues...) but these are far less important (as is real near-seawater density questions) as doing your best to keep spg about constant... by pre-mixing your synthetic water, topping off occasionally with fresh... Bob Fenner, who thanks you.

Re: Chocolate Chip Starfish ... I removed him last night when I saw absolutely no more activity from his little feet. Someone suggested it might have been a change in salinity, but salinity has been fairly constant between 1.022 and 1.023... I'm using an Aquarium Systems SeaTest Plastic Hydrometer for warm water aquariums. Can you recommend something better? or is this okay? water temp around 78F >> >> This is a fine (accurate, precise) brand, type of hydrometer. It is what I have used for many years. Bob Fenner

My fish are sick Thank you for answering my questions. I guess in my efforts to give you all the information you needed, I overlooked one of the most important things. I do have some test kits I use. The ph level is and has been 8.0 the entire time I have had the aquarium. My nitrites are and have been 0. There aren't traces of ammonia. The only thing that has changed during the time I have had everything are the nitrates. They started at 0 and after about 2 months increased to 20, after about 3 weeks increased to 40, and have stayed at 40 for the last few weeks. How do I lower my specific gravity? How do I measure it? <With a tool called a hydrometer... and it can be lowered by removing some of the seawater and replacing it with just fresh... Maybe take a look at the article on specific gravity and salinity posted at www.wetwebmedia.com> I did do a partial water change a week before everything started and I haven't been able to find a new filter for my Fluval system (small town pet shop hazard, I will end up having to order it from the internet), so I just rinsed the sponge filter out. We have well water and haven't had any problems with it, but could that have caused everything to go out of kilter? <Yes, possibly... you might consider having your water checked for you and your aquarium use... and do what I do... get a small Reverse Osmosis unit for drinking, cooking and pet-fish use> I did turn up the aeration system after I added the triple sulfa since it seemed to create a film on top of the water, and have left it up since then. Jazz did die sometime last night, as I had feared he would. He was my favorite. Thanks for the link to WetWebMedia, there is a wealth of information I will take time to read through. Also, if there is a good "Salt Water Aquariums & Fish for Dummy's" or maybe a "Guide for Panicky Pet Owners" book you recommend, I would like to have some references on hand with color pictures if possible. Again thank you for your time and advice. Sincerely, Millie Opela >> Do take a look at some kanucklehead's version of the way marine aquariums are supposed to be titled "The Conscientious Marine Aquarist"... a good read, and full of nice pix. Bob "immodest tonight" Fenner

Salinity level Last week on my 55 gal. reef tank, I noticed some corals looked strange. I immediately checked the salinity it was 1.016- I had lost water on two occasions and replaced with the fresh ro/di water that I keep on hand (no salt added yet) since one of the water loses was at 3 am and the other water loss was before 6 am when I got up I didn't think of the salt. I think that the salinity was low for 2-4 days max. I have lost a sea cucumber, blood shrimp, and all corals look very stressed. It has been a week since I raised the salinity back to normal. Will most corals recover or should I expect the worst. Anything else that I can do to Help them recover. Thanks  Art. Griffin >> Hopefully some, all the surviving livestock will make a speedy recovery... For others edification, you should almost always limit raising, lowering spg to one or two at most thousandths per day in a reef system. Bob Fenner, who says, keep an eye on your water quality in the meanwhile... if it were me I'd install a unit of activated carbon or a pad of Polyfilter in your filter flow path. Hi Bob, I have one other question for you. Is their a formula to convert temp, salinity, to specific gravity? pH ORP Temp Cond. Sal. 8.13 323 80.2 58700 38.49 8.19 317 79.7 59500 39.06 8.11 320 80.1 60100 39.49 8.14 319 81.4 60100 39.48 8.27 319 80.9 59800 39.27 8.12 316 81.4 60800 39.98 8.05 316 79.8 60200 39.56 8.03 315 79.8 60200 39.56 8.01 316 80.3 60800 39.99 nitrate 0, nitrite0, Amm very little, all most not detected Alk 5 meg Cal 425 phos .1 dKH 10 Thanks again, Larry >> Hmm, I'd rather offer a table rather than a formula here... And a warning to not get overly excited about this aspect of water quality... best to "return your water to center, or thereabouts" via water changes on a regular basis, as more than salinity is at play in figuring to or from relative density (specific gravity) or seawater. Assuming a constant salinity of 34ppt, varying temperature, the spg should read: Temp.F Temp C Spec. Gravity 86 30 1.021 84 29 1.021 82 28 1.022 81 27 1.022 79 26 1.022 77 25 1.023 75 24 1.023 73 23 1.023 72 22 1.023 70 21 1.024 Bob Fenner

SG HI BOB- Quick one on SG. What is the SG of seawater on the reef (excluding Red Sea) someone says it has risen to 1026 is this accurate? After purchasing the deep six I realized that my SG was 1016 I have raised it to 1020 over 3 days and would like to maintain it at around 1022-1023 how does that sound. Thanks Tom >> Hmm, no, still closer to 1.025 (temp. adjusted) most everywhere around the world. For reef systems, closer to seawater is better, though spg's that are lower are tolerated by most types of livestock... and there are some upsides to lower salinity... greater gas solubility, cheaper water changes, lowered disease pathogenicity... 1.022-1.023 will very likely be fine. Bob Fenner

Cause of problems within 29gal Hey Bob, If you remember my situation, all my fish were dying, but the corals were extremely healthy. I thought it had something to do with the heat, or the large addition of livestock (wrasse, tang, clown, and anemone). I finally found the culprit and it was neither of the above!!!! I am ashamed to say that I missed one of the easiest things in the marine hobby. Remember when I said that the salinity was 1.022-1.023, well it wasn't. After much disgust, I went to the local fish store and took a sample of water for the guy to look at. He tested it for ammonia, nitrate and so on, no problems there, just like my own tests. Well then he looked at the water through a refractometer, and saw that the water was 1.027-1.028. My own hydrometer had become off calibrated and for the past month I have been calculating my salinity completely wrong. I almost passed out from hearing this, notreally but I felt like it. For now on, I will clean the hydrometer more often, get it checked for calibration more often, and maybe look into buying a refractometer (very expensive). A hard lesson to learn for something so simple. Thanks for the help though!!!!! Patrick >> Ahh, a relief to hear of the cause, and solution of your difficulties... High spg is a real problem on several counts... lower dissolved gas, exchange rates, osmotic problems with livestock... A better hydrometer (to check the checker) might be one course for you to take... There are better (good enough) ones of these to be had. Bob Fenner

Hydrometers Hi Bob- Which hydrometer would you recommend. Aquarium Systems Sea Test or  Coralife Deep Six. Also should I hard plumb my w/d with the hang on overflow or use the flex hoses? Thanks Tom >> Six of one, half a dozen... they're about the same... more important in terms of accuracy and care of these measurers of specific gravity is learning how to use them... tapping their boxes to rid air bubbles, rinsing them, and storing them carefully (a zillion dollars worth will be broken today!) especially. These plastic "box type" hydrometers are better than glass types though... and accurate enough for commercial and hobby uses. Bob Fenner 

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