Nitrate test kit issue

GJW · 2026-07-11T13:33:56-0400

For a while now I have been happy with the Nyos nitrate test kit. I decided to give Salifert a try today and noticed it was showing 0 nitrates while the Nyos is reading 20-30. I want to believe the Salifert result as my Hanna phosphate checker has been trending down lately and it is also at 0. Has anyone experienced anything similar or have recommendations for me? I am aware that bottoming out nitrate and phosphate is not ideal I’m just not sure if I should increase my feeding overall or dose phosphate.

GJW · 2026-07-11T13:46:56-0400

I found an old API test kit laying around. This also shows 0 nitrates. Looks like my Nyos test kit is very off.

Dan_P · 2026-07-11T14:59:58-0400

GJW said:
For a while now I have been happy with the Nyos nitrate test kit. I decided to give Salifert a try today and noticed it was showing 0 nitrates while the Nyos is reading 20-30. I want to believe the Salifert result as my Hanna phosphate checker has been trending down lately and it is also at 0. Has anyone experienced anything similar or have recommendations for me? I am aware that bottoming out nitrate and phosphate is not ideal I’m just not sure if I should increase my feeding overall or dose phosphate.

The only way to know which test is correct, or mostly correct is to use both to measure a reference standard like Fauna Marin Multi Reference. Sorry, there is no short cut for this sort of thing.

ColorMeGone · 2026-07-11T15:02:11-0400

I use Nyos for N03, P04, Calcium, and KH and they work great.

Dan_P · 2026-07-11T15:12:10-0400

GJW said:
I found an old API test kit laying around. This also shows 0 nitrates. Looks like my Nyos test kit is very off.

Nitrate tests typically fail low, though I am not completely confident that they cannot fail high. The zinc reduction step (where you mix like mad) fails when the zinc goes bad or shaking is weak. Failing high could happen if nitrite is present AND one test kit is very sensitive to the presence of nitrite and another is not.

You really need to test a standard to know for sure.

Randy Holmes-Farley · 2026-07-11T18:21:29-0400

Is this an established tank that consequently should not have substantial nitrite?

GJW · 2026-07-11T18:39:52-0400

Randy Holmes-Farley said:
Is this an established tank that consequently should not have substantial nitrite?

The tank is almost 4 years old. I recently rearranged some rock work so it’s possible to have nitrite.

Randy Holmes-Farley · 2026-07-11T18:44:30-0400

GJW said:
The tank is almost 4 years old. I recently rearranged some rock work so it’s possible to have nitrite.

Probably not much however. The reason I ask is that if there is nitrite and little nitrate, kits will show a lot of nitrate, but the amount they show falsely from nitrite varies kit to kit.