Test kits and false results?

[Sam Hilton]

Has anybody come across the problem of ridiculous results when using NO3 test kits? I have a 2500 litre system that's showing 400ppm nitrate, up from 40ish that its been consistently at for 6 months. That 400ppm is after a 50% water change. I bought four different test kits and they're all reading very high (salifert, Tetra, hagen and Tropic marin).

No2 and NH3 are 0.2 and 0 respectively.

Also, I've checked RO and a fresh batch of salt and they're both perfectly OK.

I'm wondering if something can cause test kits to show a false high reading? There are lots of fish in the system, corals too and they're all perfectly OK.

 

[Anonymous]

Yes, you can get false reads from test kits. Sometimes there is just a "bad batch" of kits, or perhaps some other reason they go off, but it does happen.


It does seem kind of strange to me though that it would test the fresh made saltwater fine but give you an off reading on your tank. I would think it would be off no matter what you tested.

What brand of kit is this?

 

[melas]

i'll verify that this can happen too. . . heat can really mess them up. i set my nitrate test kit on my canopy over night once and the next time i tested my tank (which is usually 0ppm) it was up over 100ppm. i spent the next month trying to remedy the situation only to find out it was the kit (after i took my water and had it tested at my LFS).


always get a second opinon (test kit) when results seem really out of the norm!