I have a 235 gallon aquarium with no corals, 1 queen angel, and 3 yellow tangs. I feed a lot. I do have a refugium with chaeto but I have had the light off for 2 weeks and the nitrate went from 1ppm to .5ppm? I use nyos and api tests. They agree and I can tell by the increasing dynos that the nitrates have gone down. The phosphates are always 0. Nitrates are never over 1. Where on earth are the nitrates going? I feed ballpark 300 regular nls pellets and 300 haikari seaweed pellets a day. Absolutely no algae on rocks, some dyno on sand. No phosphate reducers and I dont change the filter sock. I do add kalkwasser. I do not do water changes.