My tank finished cycling months ago, and I still get Brown diatoms on the sand bed. This only happens during the daytime when the lights are on. If I brush the sand around, they usually disappear only to reappear hours later. I don’t think its a water quality issue because I’m well within the parameters on everything Including phosphate which is .01. Im also running Rowaphos in a media reactor. So I’m curious why I still get a layer of diatoms on the sand.