So here's the thing. My boss has a 10 gallon tank at home that keeps 3 goldfish in, one he estimates is about 4" now, and I was talking to him about what maintenance he does, and he says he never does water changes. He says last time he did a water change it was a year ago. I sent home my nitrate kit with him and he came back saying it only read 10ppm. It's a new kit and the results seem accurate on my tanks. Is it possible he is using some kind of additive that is messing up the readings, or do you think he just did the test wrong? Anybody heard of anything causing low nitrate readings?