Good question. It really depends on the fish you are raising. With Tilapia, my guess is that if you stay below 100 ppm then you are probably safe. As you push up above 150 ppm we have found that you start to kill fish. Again, we really don't know what that high number is due to the inaccuracy of the test kit. That is why we started doing the dilution test in order to get a more accurate Nitrate measurement when we have a high Nitrate count.Originally Posted by Apollo
Oliver