Api Test Kits

natalie265 · Oct 23, 2009

Everyone on this forum always recommends the API test kit. I'm just wondering if someone can tell me how you know that it is the most accurate test. I finally went out and bought one. I tested my water with the API test kit AND with the Mardel test strips. The mardel test strips picked up some nitrate (about 20 ppm). The API test was 0, 0, 0. How likely is it that my nitrates are really at 0? And aren't false positives more unlikely than false negatives? Sorry, i'm just being skeptical. (I do like feeling like a chemist with all those little test tubes though!)

MewMew42 · Oct 23, 2009

Ive personally heard that the Api test kit for the nitrate is not very a accurate!!

Although i can't help you on why it isnt, Ive just heard that...

but im sure someone will be able to tell you why =]

drobbyb · Oct 23, 2009

I would say that they are accurate enough for our purposes. Honestly, it dosen't really matter how accurate the test is as long as it's in the ballpark. After fishless cycling, testing for ammonia nitrites and nitrates becomes a color matching thing. You want to not see green, purple, or red. It's as simple as that.

natalie265 · Oct 23, 2009

drobbyb said:
I would say that they are accurate enough for our purposes. Honestly, it dosen't really matter how accurate the test is as long as it's in the ballpark. After fishless cycling, testing for ammonia nitrites and nitrates becomes a color matching thing. You want to not see green, purple, or red. It's as simple as that.

Well, Drobbyb, that's actually how i see it too. I was kind of guilted into buying this kit because people on this forum are constantly saying how "you HAVE TO HAVE the API liquid test kit", "the test strips are WORTHLESS" I don't regret buying the API kit, because, like i said, i like the feeling that i'm being scientific about it

but i am questioning if it was really THAT URGENT that i have THIS KIT.

drobbyb · Oct 23, 2009

Well, I'd have to agree on the test strips. They usually aren't even in the ballpark, and that's definately very bad.

ellena · Oct 24, 2009

I find the liquid kit a real faff to use and I'd love to have an accurate strip. I decided I would get some API strips and use both for a while and see how they compared. Until I saw the price :hyper:

£10 for 25 strips?
So, faff that they are, I'm sticking with the liquid kit.

Essjay · Oct 24, 2009

Did you shake bottle 2 as the instuctions say? If you didn't it would give a false reading. One of the reagents settles on the bottom, and all that shaking is to get it back into suspension beore use. As it's new, it's also worth tapping the bottle on the worktop before you use it to break up any solid sediment.

natalie265 · Oct 24, 2009

I did shake it, but maybe not thoroughly enough?

But my original question isn't "which is better: test strips or API kit", it's "how do you KNOW it's better?" How do you KNOW test strips aren't even in the ballpark? That's what i don't understand.

drobbyb · Oct 24, 2009

Outside of a lab, nobody KNOWS how accurate they really are, but if you take a reading on something that is a known pH, like things you might find in a chemistry class, and the API test kit measures within a tenth, you know that's accurate enough. Test strips are usually off by far more than a tenth.

Of course those are hypothetical numbers. I haven't tried that test on the kits.

OldMan47 · Oct 24, 2009

I am afraid that we do not know how accurate the test kits are. What we do know is if you follow the kit directions on a liquid type kit and then follow the practices we try to use here, things seem to work out in almost every case. If every kit we have ever used was off by 50%, the results would still work because the trial and error methods that went into our recommendations were based on those results.