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FAQs on Calcium, Supplements involving Calcium, Testing/Measuring

Related Articles: CalciumThe Use of Kalkwasser by Russell Schultz, Understanding Calcium & Alkalinity, Live Sand, Marine SubstratesReef Systems, Refugiums

Related FAQs: Calcium, FAQs 1Calcium, FAQs 2Calcium FAQs 3, Calcium FAQs 4, Calcium FAQs 5, Calcium FAQs 6, Calcium FAQs 7, & FAQs on Calcium: Rationale/Use, Sources of Calcium, Calcium Supplements, Dosing, Chemical/Physical Interactions, Troubleshooting/Fixing, & Calcium and Alkalinity, Calcium Reactors, & FAQs on Calcium Reactors: Rationale/Use, Selection, Installation, Operation, Media, Measuring, Trouble-Shooting, By Makes/Models, &   Kalkwasser& FAQs on: The Science of Calcium & Alkalinity, Importance, Measure, Sources, Use of AdditivesTroubleshooting/Fixing, Products,

Get/use "good" test kits... Hach, LaMotte, Aquarium Systems, Salifert... but whoever's you acquire, do keep up on the "freshness" dates of their reagents. Rinse all gear before and after with clean water... thoroughly mix reagents and test samples... Compare colorimetric assays against white paper backgrounds in good light.

Calcium testing... Same gear for spas?    7/9/14
Hello WWM Crew,
Thanks for all the info on this site. I use this info all the time and now I have a question that is not related to aquariums. I bought a house last fall and it came with a hot tub. Now not only do I have to test my saltwater aquariums I have to test my hot tub. I am told that I have to test for calcium hardness and it should be between 200/300ppm. Is this the same calcium that we test for in reef tanks?
<Yes it is>

And I would like to know if my Salifert calcium test kit can be used to test my hot tub calcium level.
<Yes it can be>

Would it give an accurate reading having Chlorine in the water?
<Mmm; as far as I'm aware, yes. A simple test on your part... adding some chlorine to a tested/known sample of water... could ascertain whether this is so>
Again, thanks to everyone who puts their time and effort into this site.
<Welcome. Bob Fenner>

Salt Mix or Test Kit? (or'¦Where to Find a Calcium Reference Solution?) - 02/11/10
<<Hiya Greg>>
I recently bought a box of TM salt mix, tested it for calcium (several times) after bringing it to a Spg of 1.025 and only got a reading of 300ppm.
<<Hmm'¦not the first I have heard of such findings'¦and disturbing to me for such a highly touted; and expensive, salt mix>>
I used a Salifert test kit that isn't due to expire until 2013 and has been stored at room temperature.
<<Very good>>
So I suspect a weak batch of mix.
<<Can/does happen>>
But before I contact the manufacturer of this salt mix I'd like to test the test kit.
<<Always a good course to take>>
So my question is, do you know of a way to make some homemade calcium check solution?
<<I'm sure this is a possibility, but I can't tell you how to do it. You can try searching the net re Randy Holmes-Farley (a very knowledgeable professional chemist, and hobbyist). I know he posted some formulas for home-made reference solutions'¦though I don't recall one for Calcium. You can probably also find some of his writings on Reef Central, archived in the chemistry forum>>
Or do you know of a reliable product?
<<I think so'¦ You could use the calibration fluids available for the Pinpoint Calcium Monitor. These come in 100ppm and 1000ppm flavors'¦are reasonably priced, and should give you some idea as to the efficacy of your test kit>>
Salifert does make a KH check solution but I couldn't find one for calcium.
<<Check out the Pinpoint product just mentioned'¦ You could also use multiple test kits from differing manufacturers and compare results betwixt>>
Thank You,
<<Happy to share'¦ EricR>>

Salifert calcium test   4/16/07 Hello crew, I am wondering if anybody out there knows how to get in touch with Salifert regarding their test kits. <Mmm... well, their website: http://salifert.com/ doesn't list contact information... and they're made in Holland...> I had heard nothing but good things about their products so  purchased a Salifert Ca Profi test kit from the LFS to compare a suspect API calcium test kit I have. I had  low calcium on a new tank set up  with live rock that has just been cured (API -360-380) and purchased some Seachem calcium supplements to get the Ca up. The API kit showed the CA rising to normal levels 400-460 and stabilizing at about 440. Knowing the API kits are middle of the road I wanted a benchmark to know if these results are accurate, so I purchased the Salifert kit. The first day  the new kit told me my Ca was about 370 mg/l same as the API at the time. The second day API 400 after dosing supplements Salifert 370 mg/l. third day API 420, Salifert 370. yesterday and today 440mg/l -API ,  375mg/l- Salifert. Now here is where it gets interesting, Salifert- good  API -ok or so one would think. My wife who works at a local hospital as a laboratory scientist, ran a sample of my water through a very expensive chemistry analyzer (Sundays are slow) showed calcium at.... drum roll please.... 441mg/l, dead on with the API kit. I even had her perform the Salifert test this morning  (this is what she does for a living as a lab scientist) with the same results She also pointed out to me that temperature and high humidity such as found in your LFS full of aquarium tanks could affect the reagents in a negative way and any reagents in her lab are stored with desiccants. I would like to contact Salifert  to advise them of what I found, maybe a bad test reagent(s) <Am sure they will/would appreciate this... I would write to them via their master distributors... Quality Marine in the United States, or Tropical Marine Centre in the U.K., depending on where you are... Both companies have websites, contact info. posted...> I am a bit disappointed because I've heard such great things about them and would use the test as a benchmark for the cheaper (API) test. Any info you kind folks could give would be greatly appreciated. I tried their website but it has no contact info and the box only has a European  phone number. thanks guys and gals, John P <Ahh, yes... I too have heard little negative re this companies main stream assay/kits... But as your wife states, there are many influences to the reagents... Bob Fenner>

Calcium test kit accuracy 10/03/04 I have read several of the FAQ's on calcium, and still have a question.  I have a 125g that I started Sept. 1.  I added 125lbs of un-cured LR on Sept. 11.  Euro-reef skimmer (in sump), fluidized bed.  A lot of my LR has a white coating on it - like a crust.   <assuming you have adequate water flow for curing rock (20X+ turnover of the tank?), this may simply be decay from hard curing rock> My calcium readings are off the chart (>500ppm).   <this seems very highly unlikely after even a few hours (without precipitating). Much more likely that you are getting a misreading from your test kit. Even new kits can give false readings. Do take a water sample to a friend or the LFS for a test of CA on a different type or brand of test kit> I read about the possibility of a "snow storm" and it is scaring the crap out of me.   <no worries... you would have to be/have been adding obscene amounts of Ca> I changed 19gallons of water today, using DI water - <yikes! now that is dangerous. Never, ever use/add raw DI or RO water. Always aerate for 12+ hours then buffer 2+ hours in advance of salting or using for evap water> calcium is still off the chart.   <I see... all the more reason after using demineralized water to believe that this is a misreading on your test kit> I have only added Bi-onics only once. Today I just added the Alkalinity part (part 1) in the hopes of driving the calcium down. What to do? <I'm as certain as I can be from here that you have a bogus test reading... test again my friend. Anthony>

Test Kit I would like to know your opinion on Seachem's calcium test kit , I can get it at a good price at LFS. I know you guys normally recommend Salifert brands but it is a lot more expensive. Should I pay the extra money for Salifert or will the Seachem's kit be fine? Thanks for help. <It's really a matter of preference. I have used both with good results. I find Salifert's kit to be a bit more consistent, but it can be a bit trickier to use than Seachem's. Both are excellent companies that make some very fine products. I don't think that you'd do too badly with either one. Good luck!  Regards, Scott F>

Does His Water Has More Calcium Than A Quart of Milk? Hello All, <Hi there. Scott F. here!> I'm here again with another learning project. <All part of the fun!> I'm wondering if you could help direct me in interpreting my SeaTest Calcium test kit results. I just bought this kit today and promptly tested my water, carefully following the directions. According to the test (I ran it twice to be sure) I'm running  at 1080 mg/1 Ca. <Gosh- I certainly hope not...! LOL> The test kit itself says it only tests 0 to 500 mg. So if your familiar with this kit, when you get to reagent 3 you add drops and swirl on each drop until the test water turns pure blue. <Right..> My test water started to change at drop 62 and became pure blue at drop 72, you now multiply 72 *15 =1080. <Hmm...something is definitely amiss here! A dumb question, but are you sure that you rinsed the measuring tube in tank water before commencing the test? Did you fill Reagent #1 to the mark shown on the dropper in the kit? Another possibility-Did you get all of the contents of the granular reagent out when you performed step 3? Just some thoughts.> If I understand all this, I'm very high on my Ca. Is this a bad thing? <Well, excessively high calcium could be a big problem, but you'd probably notice a "snowstorm" in the tank, as there is only so much calcium that can stay in solution. Unless you have been adding a ton of calcium supplements in a (no nice way to put it) reckless manner, or your source water contains extremely high amounts of calcium to begin with, I'd say that the problem lies with the testing procedure, expired reagents, etc. Maybe you should take a sample to a dependable LFS for a calcium test to see if they get the same result. At least this will eliminate the possibility of ultra-high calcium levels if the test results in a "normal" reading. Also, you may want to contact Aquarium Systems regarding the problem you are having. They may offer a recommendation for correction, or some other remedy for this problem> Tank is a 55g started November 16th 2002. Removed crushed coral substrate 1 week & 2 days ago and replaced with 4" DSB. (My wife suggested out that the new sand bed is probably the cause of the high Ca here). Could she be right AGAIN? :-) <Well- "high" is a relative term. There is "high" (like 400-450 mg/l), and then there is HIGH (1080 mg/l)! Deep sand beds certainly help maintain high calcium levels, among other benefits-but the level that you are recording is really unusual...Try the suggestions that I made...hopefully, you'll get things straightened out!> Thanks in advance for the help. Dave <Thanks for stopping by, Dave- and Good Luck! Regards, Scott F>

Calcium Tests-Shaken Not Stirred??? Kind Sirs, < No "sir" needed! Scott F. here today!> I have a question regarding the Calcium test kit by Aquarium Systems. Guess to be quite honest do I blame the test kit or the tester??? <It's a good hobbyist test kit, IMO. Certainly not as accurate as a LaMotte or a Salifert, but I like it myself> I thought I read that on the site, that although it's not one of the best, it is an inexpensive test kit to help monitor calcium levels. <Yep> It happened to be carried by my LFS. But testing for the past week (first time calcium tester) I haven't been able to get a reading below the 500 limit. The test never changes over to its "true blue" color. If I may go through the >process. Step 1 small vile of tank water, seems easy enough, taken from the top of the tank to prevent hands from entering the tank. Reagent 1 to line indicated, again thought I could handle it, do shake reagent before filling dropper to mark line. Reagent 2, dated March 04, figure still good. Swirl to mix. Should this be stirred??? <Nope- just swirled> Then adding drops of reagent 3. Directions indicate swirl after each drop? <I'd swirl after each drop> Usually  swirl after adding 5,problem??? <This might be> Also should this be stirred??? <nope- I wouldn't stir> A brief supplementation history: Tank 30 gal, about 20 lbs of live rock, upon recommendations of LPS, when purchasing last few lbs of rock, Bought and used Kent calcium, Kent Strontium and Kent Essential Elements. Up until that point I never supplemented anything to the tank. (4 years). Found your site, learned about the ion problem of calcium chloride, strontium supplementation is not really required but still use the Essential Elements to add iodide to the tank (for cleaner shrimp), <I think that you'd do better to just make frequent (2x weekly) small water changes. If you are going to use additives, you need to test for them> Added calcium, a capful every 4 days up until 2 weeks ago (for about 1 month total), I was going to finish the bottle, figured with water changes and only using calcium chloride about 3 to 4 months I wouldn't have an ion problem. (But I learned that I should test before supplementing so I stopped adding until I can get the test kit figured out.) <Great move on your part- you will not regret doing it this way> PH always test around 8.4, no variation between day and night, figure it's the new (closed) house situation that I read about. And alk is always around 3.4 meq. I think it's on the low side, <Actually, that's a good reading, IMO> only buffer added is Red Sea Buffer  that came with the test kit, added to Water change water (not to tank) after instant ocean salt added and aerated overnight. <Good technique, aerating the water before use, particularly if you're using R/O> Not sure if any other tank condition would affect the test. Water changes are 4 gal every two weeks. Also, does SeaChem Calcium have a shelf life? <Yes it does- I'd consult them for specifics (see the link to them on our site> LPS has a few small bottles, (it mostly carries Kent products), and from the dust covering looks like it's been there awhile. Figured I'd switch to SeaChem after using up the Kent Calcium. The only calcium requirements I have for my tank at the moment is for Coralline algae growth. <Seachem calcium is Calcium gluconate, and this stuff will grow coralline like crazy, if used correctly. I'd use Seachem's test kit if using this product, by the way> Coralline consists of  some purple and green growth (little) some bleaching but leaned that's from improper dosing. Think it's form lack of, not excessive. <Lots of reasons for coralline declines> The only other calcium test kit available from LPS would be Red Sea. Would it be worth purchasing and testing or should I look to purchase test kits online? I'd stick with the Sea Test for now, and switch to the Seachem if using their calcium product. (would like to avoid if possible-tank spending monitored to easily) Temp is a steady 78 degrees and salinity is 1.021. <Sounds fine> Thanks for your help, DaveK <Well, Dave- sounds like you're on the right track...Just keep thinking about making your hobby as simple as possible. Unless you have very specific reasons, I'd avoid using lots of different additives. Remember, the adage that we both touched on "don't add something to the water unless you are going to test for it". In many cases (there are, of course, exceptions), simply executing regular water changes can provide all of the trace element replenishment that you will need to maintain a healthy system. If you keep things simple, you'll enjoy your hobby so much more, and will really be successful in the long run! Good luck! Regards, Scott F>

Calcium Level Hi Bob, <Anthony Calfo in your service> I'm having a problem along with everyone else on maintaining my calcium level. Currently it's been 700+.  <this is almost certainly a misreading my friend... if not an outright impossibility. Crystalline precipitation of calcium carbonate begins easily in most tanks by 500ppm. Anything over that is very difficult to even achieve. Do test this water with an entirely different brand of test kit. Try Aquarium systems ReefTest kits> I read your FAQ's and found that if you add backing soda to your Reef Tank, it will lower your calcium. However, it will raise you pH level.  <fast and temporarily... easily abused too> I have lost a lot of live rock and other creatures and I'm getting frustrated. Would you please give me some help on keeping my Reef Tank in proper condition such as the levels and what type of chemicals to use in maintaining my Reef Tank? God Bless, Peggy <no worries, my friend. I suspect your primary problem is the test kit, not the water. You could only get such readings by a repetitive and obscene overdose of calcium supplements. I discuss water chemistry for ref aquaria extensively in my book (http://www.wetwebmedia.com/bkcorlproprev.htm). If you are really ambitious, do pursue the works or Dr Craig Bingman... very learned and informative in his studies on water chemistry. Anthony Calfo>

How to measure Ca Hi, I hope everything is doing well with all of you! <and you as well, my friend> I was reading the procedure recommended by Anthony in his book, and its sound easy, but I have a problem, I can't find reliable test for Ca.  <indeed... the liquid titrations are tedious and not clear. To some extent they are variable due to the differences in each of our eyes to perceive colors. But some kits are just plain inconclusive. For an inexpensive and reliable kit, I like Aquarium Systems brand> The first day I measure it with a Red Sea (liquid) reagent and it shows 300 ppm (scale from 50 to 50) that nigh I dosed one glass of super ultra archi full loaded and hypersaturated solution of Kalk (wink as Anthony says) the very next day I use the meter again and it show only 300, so that night I dosed again another glass (concentration 1/8 tea spoon) the next morning the same... 300, so I repeated everything but the same reading 300... The Ca is going up, I'm sure, because the red algae is growing at a seeing rate, my 3 shrimps are changing its skeleton, and my only Halimeda bush increase at least one leaf at day... <excellent... and agreed. The Ca is certainly going up. I have heard many complaints about the Red Sea test kit specifically.> I know you can said that my tank consume 50 ppm by day, but I'm not sure at all, you will see my tank is not full (I presume) of Ca demanded inhabitants <yes... 50 ppm is really a lot! It is unlikely that the demand is that high although possible> 200 lts (50 gallons) 35 pound live rock (almost with nothing over the rock) 2 small (1 inch) cinnamon shrimp (cleaning family) 1 medium (2 inches) boxing shrimp 4 turban snails (their are growing since I'm using Kalk) 2 damsel fish 1 yellow tang 1 little colony of small polyps a spot of Halimeda and... nothing more <yes... agreed... not 50ppm daily demand. The test kit is certainly inaccurate here> PH 8.3 (average) Ammonia 0 Nitrites 0 Nitrates 0 Temp 82° I don't want to dose more Kalk until I have a correct way to measure the Ca. I don't want snow storms... <very wise> Here I only found Red sea Reagents and they are liquid not dry as Anthony's book recommend,  <hmmm... that's OK. I can live with a liquid reagent if it is fresh and rotated often (do not keep longer than 6 months)> exist an digital device like PH meter from Hanna or something more accurate to read Ca?  <too expensive> there is another way to know how much Ca my system is using?  <yes... even with a less accurate test kit it is easier to test the daily demand by starving the tank of calcium for several days: test the Ca before you start, then test it several days later and divide the difference in drop by the number of days you went without dosing Ca. This gives you a more reliable reading> there are indirect methods to know if the Ca is too high (like high PH?) how many angels can I seat in one square feet? <heehee... unfortunately the indirect methods are not always reliable. Let me know what other test kit brands are available if you cannot find Aquarium Systems (the maker of Instant Ocean Sea Salt). Also, some of the big mail order companies here in the US frequently sell overseas like Marine Depot. Perhaps you could inquire about a special order if necessary> Thanks for your prompt answer, Carlos <with kind regards, Anthony>
Re: Calcium Question
I am using SeaTest and Salifert test kits for calcium. I also took some water to the LFS today and they said my levels of calcium were at 270ppm. You said I might be dosing too fast? I am dosing about 1 1/2 liters of freshwater with 1/2 teaspoon of Kalk at about 1 drop per second at night. I am dosing it into my sump right next to the inlet <fair enough... sounds slow enough for dosing. We've exhausted the likely causes. Do test your magnesium levels to see if they are skewed with Ca/Alk. Magnesium should ideally be about triple Ca (1000-1200 ideally). Best regards>

Calcium and Test Kits Crew, <<Greets...>> I just wanted to add my observations to the discussion on today's question and answer page about calcium concentration and suspect test kits. I thought I had the same problem earlier this year. I was beginning to add calcium to an 8 year old tank (FO) to which none had been added before and was monitoring calcium and alkalinity. Calcium levels were not rising (alkalinity was improving) and I suspected either 1 the test kit, or 2 my forest of cancerous Halimeda. Through persistence and continued monitoring I have finally gotten the level up into the mid 300ppm (Salifert kit) and my alkalinity is maintained around 10dKh. It has taken months and nearly a gallon each of ESV's two-part product! <<Time for a calcium reactor...>> My explanation is that the tank has been deficient for so long that the substrate and live rock have absorbed it back to reach "equilibrium" levels. Am lost as to what else it could be - the fish? <<Not the fish either, just not really possible to pour in calcium and get a perfect reading in one day, and quite likely the forest of Halimeda was sucking it back out just as quickly as you put in the calcium. Sometimes very hard to get ahead of demand.>> I have also noticed that at least for my system, the alkalinity moves much faster than the calcium when using this product. Given that the two measures are inter-related, calcium has a lot more 'momentum' in the reaction equation than alkalinity. Thanks for the great work you folks do! <<Glad you find it helpful.>> David <<Cheers, J -- >>

Calcium Hi Bob, I have a question for you re: calcium, if you have the time. We have a calcium test kit from a company called "Hagen" the test name is Ca Test. When we perform the test, the readings are off the chart, over 800 ppm. We add no calcium to the water, however, we live in Montana and our water source is the Missouri River. Much of the river runs through limestone canyons. In your opinion, do you think that it's more likely the test is inaccurate, or would you think that our calcium could be that high?  <This is very high... but possible... Yikes, "liquid rock", even rockier than good ole San Diego...> The reason I question this is because our purple coralline algae looks like it's bleaching out. <Actually not surprising... think about this. The corallines require both high alkalinity and biominerals (like Ca)... but too much alkaline earth (e.g. calcium) will greatly reduce alkaline reserve... Ah...> To refresh your memory, we have a 125 gallon tank. Our lighting is 3, 175 watt MH and 2, 160 watt actinic. We run a Berlin style filter with a Turbo Flotor foam fractionator and a wave maker. I think my lighting, filtering, skimming and water movement is good. Do you think we could actually need to add calcium?  <No> Throw away the test kit? If you think that this test kit is inaccurate, could you recommend one that would be reliable? <Maybe have a shop "test your tester"... but it may be fine> All of our other readings are good, with the exception of our PH. Our PH has always, for the 5 years I've lived in Montana, been a little on the low side. Never as low as 7.5, but never a good strong 8.0, probably somewhere in the vicinity of 7.8 if I had to guess. Even with water changes we can't make that figure budge. Is there a relationship between the two? I read your web site religiously and your column in the fish Mag, but get a little confused. BTW, I'm a San Diego native, transplanted to Montana due to job relocation. Thanks for any input you care to share. Betsy >> <A few possible relationships at play here... If it were me/my system and home, I'd just get and use a decent reverse osmosis filter system for making water for aquarium use as well as cooking and drinking... Do look into one of these (Home Depot, Lowe's... or pet-fish relabeled brand... And don't think about not-so sunny Cal... the traffic is horrendous here (even for dodgers like myself who rarely venture out), and folks are becoming way to mean, small-minded for my blood. Bob Fenner>

Calcium Problem A strange one, Bob. Began using the Salifert Calcium test a few weeks ago. My level jumped in the last two weeks. Here are the overall readings: Ammonia - 0 Nitrites - 0 Nitrates - 0 Ph - 8.2 Salinity - also jumped to 1.032 <What?> Calcium - went from 450 to 1000 <Nah. Something awry here> Have begun slowly bringing the salinity down with partial water changes, over the last four days, presently down to 1.028. However, the calcium still is around 1000 mg/l. We ceased adding anything that contains calcium two weeks ago, and have been using only Coral Vital and Kent's Invert twice a week. I have been unable to find the cause of the additional calcium. I now have the following live stock: <Stop right here... and stop using the sugar/vital product(s)> yellow tang royal Gramma six-line wrasse green Chromis yellow-fin damsel yellow-tail damsel percula clown long-tentacle Anemone peppermint shrimp emerald crabs Hermits snails pagoda cup frogspawn mushrooms bubble finger All appear fine except the bubble and finger, though both are coming back around with the partial changes, 2 gallons of fresh/day, no saltwater mix added. I intend on going to a 10 gallon change tonight, and bring the salinity back down to 1.025, but still am concerned about the calcium. Any ideas?? Rick Farris <There is a false positive with the Salifert Test... you will soon be about right... just drop the Weiss... Bob Fenner>

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