# Scientific analysis of popular test kits



## banderbe (Nov 17, 2005)

Why is it that nobody has conducted a scientific comparison of hobby test kits?

It seems like it should not be that difficult to create a water sample with a known quantity of NO3, for instance.

Then test Red Sea, Salifert, Aqua. Pharm., La Motte, etc.

It might take a little cash to get all the test kits, and equipment to accurately create samples, but I bet people on this forum would help out with a small contribution if someone with a background in science/chemistry would be willing to conduct the experiments.

I know the common belief is that La Motte is the most accurate and that's probably true but what about the others? I'd like to know if the Aqua. Pharm. test kits I use aren't as accurate as Red Sea in detecting NO3.

And I would bet some brands are better at detection of some things like KH than others are. I could see myself having a collection of test kits from a variety of manufacturers based on these results.

Also, it may be that some test kits are more accurate at lower levels while others are more accurate at higher levels, etc.

Anyway I am just throwing this idea out there.. I doubt anything will come of it but there it is..


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## RTR (Oct 28, 2005)

The aquarium mags have posted some articles comparing test kit performance on standard solutions in the past. You might check into their archives and get reprints. 

You should add Hach to LaMotte on the high-quality kit list.


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## plantbrain (Jan 23, 2004)

But........even the best brands have some variability, the cheaper brand might work well for you, but another person's may not, even if they are made by the same company. User error adds up, expiration dates for the reagents also can play a role. Many test kits for NO3, pH, PO4 offer wide ranges, often too wide to do much other than hit a ball park figure.

So even if you did all the work, you are still left with these issue.........

Even the best Lamott and Hach test kits have a an error of 1-5ppm of NO3 over a 1-20ppm range.

That's pretty large.
You should calibrate the test kit you use and then try 3 ranges, say .3 ppm, 3.0 ppm and 30ppm. 

Regards, 
Tom Barr


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## JaySilverman (Jun 19, 2005)

I calibrated my Aqua pharm No3 and Po4 and they were spot on in the lower ranges. When things strated getting higher then 20 ppm it was harder to tell.


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## John N. (Dec 11, 2005)

I've test the AP kits and LaMotte Kits using my water quality lab equipment and machinery (colorimeter, reagents, etc). LaMotte kits are the most accurate between the two. But each have it's own variability based on expiration of the kit, enviromnental exposure, etc. So there's really no point to testing it to determine which one is going to give you the most accurate results.

The only way to get seemily accurate results are to compare each test with another test and if its different, get another test kit to break the tie. 

Probably the answer you wanted to hear, but that's the way it goes with variability in these test kits. But they serve our purposes and give us a general ballpark of the system's water parameters. 

-John N.


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## Laith (Sep 4, 2004)

Yes, given all the variables that come into play, the only thing that gives some re-assurance on the results of a test kit (or convinces you to throw it out) is to do your own calibration on the test kit you have. And re-calibrate if alot of time goes by between uses or when you run out and buy a new test, even from the same company.

I test a lot less than I used to, usually only if I'm seeing something strange. But I used to calibrate with known concentrations and if it was way off with a new test kit I'd take it back to the lfs and they'd replace it.

I even calibrate when using the LaMotte kits and I have seen some of them give results that were way off too.

By the way, the Seachem test kits all come with a reference solution that you can use to test the test kit with. Avoids making your own...


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