First, what are you testing with?? If it's the API test kit, then you may
actually have 0 ammonia. The test doesn't come out as brilliant a yellow as you see on your color chart. The main thing you are really looking for is a "lack of green", but it can still appear closer to the 0.25 than the 0. The best thing to do is a side-by-side test with your tank water and either RODI
or distilled water as a control sample..... something you KNOW has no ammonia in it. If the colors are the same, then you're good.