Originally Posted by Bettaorr
Nutrafin master kit
I'm not familiar with that test kit. But my thinking was that if that's as high as the test goes, your readings may be off the charts and another water change of around 75% is needed. That, or the tests are malfunctioning. Are they expired? I'd do another water change to be safe.
First, fill a test tube with half tank water half tap and test it to mimic a 50% water change before you do it. That way you get an idea of how much water you need to change. Also, what are the levels in your tap water?