Test kit accuracy.

[Ninong]

I have been very frustrated lately trying to test my tankwater and my ASW prior to water exchanges and I thought I would share some of this frustration.

I decided I would test for more than the usual alkalinity, calcium, ammonia, nitrite and nitrate. So I purchased test kits from a well known and reputable manufacturer to test for iodine, silicates, phosphate, copper, boron and magnesium.

I found that the test kit for iodine was incapable of measuring any level of iodate at all. It gave me a reading of 0.06 ppm iodide and totally undetectable iodate. I verified the reagent batch numbers with the manufacturer to verify that they are still fresh. Even though the manufacturer's ads proclaim "no interferences," the excuse given by the manufacturer is that there are probably some interferences at work. I found several reports from others with the exact same problem with this test kit. They got readings on iodide but zero on iodate. As far as I am concerned, this test is totally unreliable.

I tried to test for boron but the result was too high to be taken seriously. According to the test, my boron was >250 ppm. I checked with the manufacturer and found that this particular boron test kit has not even been produced for at least six years. According to the online vendor they received it from the manufacturer's main U.S. distributor only two months before they sold it to me. I am waiting for the manufacturer to send me a replacement boron kit. They told me it was shipped from California more than two weeks ago but I haven't received it yet.

I tested for magnesium and I don't know whether to accept the results as accurate or purchase a different brand of test kit and compare the results. The problem is that I am using what is reputed to be the most reliable magnesium test kit available and any measurement with a "lesser quality" kit might only confuse the issue. I have decided to re-test weekly using the same test kit to see what my readings are before jumping to conclusions.

Phosphate, silicate and copper were undetectable as expected.

Right now I am using LaMotte for calcium and alkalinity and Salifert for everything else.

I did a little online searching and found this very interesting recent (July 2003) study by a German reef club: http://www.korallenriff.de/nitratmessung.html

It's in German but the numbers are in English!

You will notice from the chart that they purchased a 50 mg/kg (ppm) stock solution of nitrate from Merck. They prepared three samples for testing: 17 ppm, 2 ppm and 50 ppm. They also included a sample of tankwater from Robert and Manuela's reeftank that they believed to be ~20 ppm. These four samples were tested by three different individuals who had no idea in advance what the solutions should measure. All they knew was that they were to test for nitrate using eight different test kits plus a $170 Hanna photometer.

The results were surprising and very disappointing. The Hanna meter was nowhere close in it's measurement: It gave a reading of 3.5 ppm for the 17 ppm sample, 0.0 for the 2 ppm sample, 15.9 ppm for the 50 ppm sample and 8.4 ppm for the tankwater that was actually 20 ppm.

The Tropic Marin (nice German brand) test kit was a complete joke. It measured only 1 ppm in all of the three test solutions and 5 ppm in the tankwater sample. Yes, incredibly, it measured exactly 1 ppm NO3 in samples that were known to be 17 ppm, 2 ppm and 50 ppm.

The Salifert test kit was reasonably accurate, allowing for individual interpretation of the color charts.

I thought I would buy a bunch of test kits and test my ASW after three or four days of aging to see if I could either verify or dispute the manufacturer's claimed analysis but at this point I wouldn't dare publish any results because I have little confidence in the accuracy of some of the less frequently used test kits. And not that much more confidence in the others. I think Salifert's iodine test kit is a complete waste of money and I will reserve judgment on their boron test kit until after I receive one that is less than six years old. I'm not sure what to think of their ammonia test kit. I'm sure it is helpful if you are testing a newly set up aquarium during the first week of the cycle but after that period is over what good is an ammonia test kit that cannot measure below 0.5 ppm total ammonia? Notice that their ammonia color chart does not read "zero" or "undetectable" for the first color match (white), it reads <0.5 ppm. That's because the test is incapable of testing below 0.5 ppm total ammonia with any degree of accuracy.

[Reefland]

Hey Ninong!

I can't say that I am surprised at all; more aggrivated than anything. What is really discouraging is that we chase our tails in circles based on the results of these test kits and not knowing what were chasing is a real pain.

It makes one think though especially about the nitrate since that is a big one for everyone. If we are measuring with our test kits, high readings of like 50ppm, we start taking measures to correct the unsafe condition. However if we measure with our kits, readings of 10ppm, we typically don't raise a big stink and no action is taken. Based on the results you mention, we should be taking reactive measures just as we should with readings of 50ppm! How do we really tell when something is unsafe? You can't rely on the appearance of our animals because they can appear fine for several weeks and longer with high nitrate levels but long term the affects are fatal. Obviously we can't rely on the available test kits. What gives?

Later,
Scott Z.

[Ninong]

Scott,

Do you remember Robert (KORALLEN) from a couple of years ago? According to his profile, he posted 32 times but I guess they were all lost when you switched software? We were trying to carry on a dialogue with him using Babelfish as the go-between and the translations were hilarious. I think Joaco made sense of some of them for us since he speaks German. Anyway the thrust of the threads was that he couldn't understand why Americans didn't use Nitratreductors like they do in Germany. I think he may be an agent for Aqua-Medic or something. ;;

Anyway... That was his website http://www.korallenriff.de/enter.html that I linked to above. Looks like he has gone "commercial," if you know what I mean. His site is interesting because he has pictures of reeftanks and equipment rooms of several dozen German hobbyists -- click on Aqua-Bilderbuch.

[kevinpo]

For the nitrate test at least all of them detected nitrates (except for the Hanna meter at 2 ppm). From that I would make sure to keep my nitrate levels testing at zero. You could be fairly sure they were at least low. I have been unable to get a reading using Salifert on my tank but with some large clams and 20 lbs or so of macroalgae in the sump they may be using all of the available nitrate. I no longer test for anything except calcium and alkalinity.
It makes you wonder about the people who spend a small fortune on all the different probes to monitor various things as to their accurracy. Test kits are expensive enough.

Regards,
Kevin

[Ninong]

For the nitrate test at least all of them detected nitrates (except for the Hanna meter at 2 ppm).

Kevin,

Some of them gave a reading of 1 ppm on a sample solution known to be exactly 50 ppm. Some of them gave 10 ppm, 12 ppm, 25 ppm, 30 ppm, etc., on that same 50 ppm control solution. The results with the 17 ppm sample were not much better. I don't think a reading 1 ppm or 5 ppm is of much use if the true NO3 concentration is 17 ppm.

For the first several weeks I was consistently getting readings of 0.05-0.1 NO2 and 25 ppm NO3 but my readings for the past six weeks or so have been 10 ppm NO3 or less. Lately my NO3 is around 2 or 3 ppm. I get no color at all on the NO2 test when looking down from the top of the vial but I do see some slight pink when looking through the side with the vial pressed firmly against the white background. Dividing by 10, that gives me a nitrite reading of about 0.025 ppm. So far I have not had a perfectly clear nitrite result when looking through the side. That's using a Salifert test kit. I'm not really concerned with a reading of 0.025 ppm NO2 or a reading of 3 ppm NO3 but I do wonder how some many people report zero NO2 and zero NO3 on tanks that are only 3 weeks old. I have a feeling that they are using poor test kits or their eyesight is even worse than mine.

I don't know what to make of the Salifert ammonia test results. I discussed this with the manufacturer and was told that a cloudy result was not a problem unless it was slightly tan or yellowish and that the test could only measure down to 0.5 ppm total ammonia. Anything below that should be described as either <0.5 ppm or undetectable (by their test).

[saltwaterdave]

Intresting thread and I am glad this has came up,because I have been having the same problem the last few days.I purchased a salifert ph test kit and a Aquarium Pharamaceuticals Ph test kit.I have always heard Salifert was the best so when I tested it with that test kit I got a reading of 8.0 .So I made corrective measures to raise my ph a little.Checked it the next day and it was still 8.0 according to the salifer test kit,so I made some more corrective changes to adjust my ph.Checked it today and according to salifert it was STILL 8.0.I got out the A.P. test kit and got a ph of 8.4 with that test kit.So basically I have no idea where my ph is.
I also had a similiar problem with the calcium test kit.With the salifert test kit it was showing Ca levels of over 500 with a Red Sea test kit I got a reading of 450.That was yestreday,today I got a Ca reading with the salifert kit at 490............So to be honest I am not sure what is what.Before the hurricane wiped out my xenia,I use to watch them and they told me when something was out of wack,and they were always right
Salifert says my alk is at 5.60meg/l which I think is a little high.So for a couple of days I am not gonna drip and kalk and check things out then.I do not really have any other alk test kit that I trust,my other one just says high,Good,low,........with a color chart,so I don't trust it.
David

[Ninong]

David,

It would be perfectly normal to get a pH reading of 8.0 early in the morning before the metal halide lights come on and then get a reading of 8.3 or 8.4 late in the afternoon before the metal halides go off. I wouldn't be concerned unless the early morning reading was 7.9 or less. I wouldn't worry about the late afternoon reading unless it was above 8.5.

An alkalinity reading of 5.6 mEq/L (15.7 dKH) is a bit on the high side but it's not high enough to cause problems unless it affects your ability to maintain adequate calcium levels, and that doesn't appear to be the case. I try to keep my alkalinity between 10-12 dKH and my calcium between 425-450 ppm.

I have no experience with Salifert's calcium or alkalinity tests because I'm using LaMotte. The only reason I got LaMotte was because everyone was out of Salifert at the time. Now that I have used the LaMotte kits for calcium and alkalinity I would not even consider anything else. I have been less than thrilled with Salifert's responses to my questions regarding problems with their test kits. I pointed out to them more than a month ago that the boron test kit I was using was totally wrong and they agreed to send me a newer version. In fact, I was told more than two weeks ago that the new boron test kit was on it's way to me from California. I still don't have it and I don't have a reply yet to my inquiry of three days ago asking if it was coming by Pony Express. According to the large online vendor who sold me that particular test kit, it was only in their inventory for two months. They claim they just received it two months before from Salifert's main U.S. distributor. Yet Salifert admits that they haven't even made that version in more than six years. It makes you wonder how fresh some of these test kits really are. Salifert claims that they are now putting expiration dates on their reagents. They told me that they started doing that several weeks ago.

[saltwaterdave]

All the ph readings were done at night and my main concern was making adjustments for 2 days and the salifert test still reading 8.0 after each days adjustment.It still said 8.0 today.My ph test kit from salifert does not have a expiration date my my calcium test kit does.
David

[Minh Nguyen]

Ninong,
Like Kevin, I only test Ca and Alkalinity using Salifert test kits. I do hav some old Red Sea test kits also and find that the Salifert give consistently higher number than the Red Sea test kits. I am not sure the exact numbers are in my tank but try to keep it somewhat constant. The tank did fine, so I don't bother to get more presise .
FWIT, testing for various chemical is not all that easy unless one spend lots of money. Even test for Blood Sugar with a 100.00+ tester and 3 dollars per tes only give result within 15% of actual value (can varies by 30% from one tiem to the next)
Minh

[Ninong]

Minh,

The main reason I purchased a bunch of test kits is because I am concerned that we may not be able to count on the claims made by the various salt mix manufacturers. The recent threads about extremely high alkalinity in some batches of Instant Ocean and the mystery surrounding the reported bleaching that some hobbyists experienced when switching from Instant Ocean to Crystal Sea Marinemix have caused me to want to be more careful about what I put in my tank BEFORE I put it in, so I thought I would test the saltwater before it goes into the tank and compare that with the tankwater readings on various elements to see how they vary over time. However, I am finding out that the test kits themselves may be as unreliable as some of the manufacturer's claims for their salt mixes.

Richard Harker just did an ICP analysis of Crystal Sea Marinemix Bioassay Formula and posted some of the results here: http://reefs.org/phpBB2/viewtopic.php?t=39962

Inland Reef has been promising to commission their own independent analysis of the various salt mixes for the past 8 months now but they still haven't started.

[zhenya]

George,

All the metals aside and just taking Ca and Alkalinity in consideration,what was your tests results on the freshly mixed CS biomix,say after 24hrs of aeration or so? The reason I ask is becouse I'm due to do a water change in my 75g tank and I desided to open a second box of the salt and use that this time.
I went out and bought brand new test kits for KH and Ca(Salifert),the Ca test kit was manufactured in July 03 and exp. date is by 07/08 and there is no dates on the KH test kit.

Here are the tests results for those two values after 24hrs, Ca-380ppm and Alakalinity - 11.8dkh
I then used the same test kits to test my tank water for comparison and results are: Ca- 525ppm and KH is 14.4dkh. I'm not sure what to make of this results becouse having both of this values this high seems unreasonable with the demand that I have in my tank.
FWIW, the first box of CS salt that I was using measured consistently at KH-15-16dkh and 390ppm of Ca respectively. It is a bit different from the second box but I think it is still consistant.The tests of tank water have me buffled though-could alk and Ca be this high at the same time?

[Ninong]

Gene,

I have confidence in my LaMotte calcium and alkalinity test kits. I have been testing my tankwater at least twice a week since I set up my tank four months ago. For the past two months my tankwater has tested consistently between 423-454 ppm calcium and between 10.5-11.7 dKH alkalinity. Therefore I have not been too concerned about testing the Crystal Sea Marinemix Bioassay Laboratory Formula saltwater prior to using it. The last time I did that was about three months ago and the only thing unusual was the measurement of alkalinity. IIRC I tested for calcium twice, a few days apart, and got readings of 392 ppm and 372 ppm. Both alkalinity tests were in the 15 dKH range. I was told by the manufacturer that my alkalinity reading was probably influenced by my source water. My tapwater measures 8.5 pH and I was using a cheapy portable D.I. filter that produces product water with a TDS reading around 67 ppm. The unfiltered tapwater measures 172 ppm TDS.

I decided that I would wait on testing the freshly made up saltwater until after I had a proper R.O./D.I. system in place and had test kits on hand to test for as many different things as possible at the same time. Well I have the proper R.O./D.I. system and I have lots of test kits now but I'm afraid that the R.O./D.I. system is not yet installed because I'm having a difficult time working that into the area where I would like to have it and I've been holding off on sticking it out in the garage where my brother-in-law thinks it should be. I'm also trying to use up the four D.I. filters that I bought with the portable D.I. unit. I don't think my tapwater is really a problem for a saltwater tank anyway and I think I could actually use it with just sodium thiosulfate drops to kill the chloramines if I had to. I have tested the tapwater for copper, silicates and phosphates and all of those tests were fine.

I will probably test my saltwater after I start using the new R.O./D.I. unit but even then I may not be comfortable publishing the results because I do not have that much confidence in some of the Salifert test kits that I have already used. I have zero confidence in my present boron test kit, the iodine test kit cannot measure iodate and I question the reliability of the magnesium test kit. I may test my saltwater for magnesium but right now I don't have any saltwater made up. I did test my tankwater for magnesium a few days ago and got a reading of 1050. I'm not sure whether to believe that result or not. That was just one test. I'll test it again perhaps once a week and also test the freshly made up saltwater to see what I get. But even then I don't know whether to believe the results or not. As you probably know, I did send a sample of my salt mix to the manufacturer about three months ago and I have their certified test results for that particular salt sample. I asked them to test for calcium, alkalinity, boron and magnesium. The results they gave me were very close to their published results. I have no reason to doubt the accuracy or truthfulness of those results. I would be more inclined to doubt the reliability of my testing abilities and/or test kits.

[zhenya]

I too question my testing abilities when it comes to adding "level" spoon of Ca-2 reagent and always question my results becouse of it.I figure if I'm consistently adding too much or too little the results should be consistent but accuracy...well that is another matter. I don't understand why it couldn't be packaged in a small individual packets? I can be confident then in one thing that I'm being precise and conducting the test properly to have any sort of confidence in the results

Well,I just switched out 5g of water in the tank and so far only my pink Pocillopora colony had retracted its polyps and had not returned to normal yet.
I hope nothing else happens when I change 5g more tomorrow morning.

Water changes scare me lately,George
In regards to testing for boron and iodine,I gave up earlier this year when I couldn't find any of this test kits and now from reading your thread I don't think I'll conduct any with the over the counter kits-I think it's useless. I wonder if my water company would be willing to run those tests for salt water,for the price of course...
FWIW, none of those test kits are cheap and not to have confidence in them is disapointing to say the least.
I thought for some reason that you had installed your Ro/DI unit where you wanted...also,did it come with all the fittings to make connection to the house plumbing? Mine didn't and I had plumber rig up some valve(manual ) but hopefully I can set up something automated this spring.
FWIW, my topwater measured at 212 TDS but 0 comming out so I'm at least happy with that ;)