pinkfloydpuffer

Hi
I'm using the Mardel 5 in 1 test strips to test the water quality in my tank. I have a 20 gallon brackish tank with an AquaClear filter, which uses foam and carbon to filter the water. The nitrite test works fine, but every single time I read the nitrate, it reads at 30 PPM, so I never really know when the water needs to be changed. I was wondering what could be causing this problem, and if there's any way to fix that. And if not, what other kinds of nitrate test that would work.
Thanks.

Lucy

The test strips really aren't accurate.
If you can get the API master kit. It lasts a long time and it's very accurate.
Toss the strips.

Edit: If that is a true nitrate reading, you can bring it down with extra water changes. Once a week is usually recommended for maintenance.

pinkfloydpuffer

I really doubt it's the correct reading, cause it says 30 every single time. Even when I measure right before and right after water changes. I change 25% of the water a week.

pepetj

Hi pinkfloydpuffer: I use both, strip test (for quick screening) and liquid reagent test (for accurate readings).

For some reason I have found that strip test don't work well for nitrates at the lower end (40 or 50ppm down). Readings at this range are likely false positives (I have double checked with liquid reagent tests -Marine Enterprise, Tetra- and found 10ppm or less when the strip readings where at 40ppm).

I have seen this with both the Tetra 5-in-1 and with Jungle Nitrites/Nitrate strip tests. You seem to be reporting the same phenomenae with the Mardel brand strip test.

I don't find strip test a bad product, just see them as screening (not diagnostic) tests.

At least for nitrates, but maybe for other variables too, it is unlikely they will produce false negatives (which means when something is not measured by them, there's a good chance it's not there) but they are prone to false negatives (at least at the lower end of nitrates, -but also at water hardness in my experience- presenting a finding that is not really there).

Pepe
Santo Domingo.

pepetj

Erratum: should read false positives, not false negatives

Pepe
Santo Domingo

pinkfloydpuffer

I bought a liquid test today, and it read at 0, not 30! So I'm pretty sure that this one will work for me. Thanks for your help everyone!

Lucy

What test did you buy? If your tank is cycled it really should have some nitrates showing.

The thing with the API nitrate test bottle #2 is you rally have to shake it, bang it and abuse it to get it the crystals mixed together or you could get a false reading.

It might be a good idea to re test it.

pinkfloydpuffer

It's the API test. I'll go ahead and test it again tomorrow.

Lucy

Ok, really whack that #2 bottle around. lol

pinkfloydpuffer

Smack!