I have ridiculously high nitrates straight out of my tap from a borehole - over 400 ppm (test kit can't measure any higher). I've been using this in my small tank for a year now. I have an angel fish, 2 glass catfish, 3 corys, a red-tailed black shark, and until recently, a tire-track eel (re-homed him as he was getting too big), as well as some tetras and plants. All the fish appear healthy.
Last week I measured the nitrates from my Brita filter jug - 20 ppm. So now I filter the water before I top up. So 20 ppm for me is a dream come true.
