ok, then you need to do another water change of at least 50%, wait half an hour and re testOk the change has been made, waited half hour and done a api test.i would do a bigger change than 50% but its your tank and your fish.... re test the water in about 30 minutes, this will give the water time to mix giving a more accurate reading. if its still not at 0 then another water change is needed. the 0 reading will be bright yellow if its anything else then dont convince yourself that its ok
The result is:
0.25








