I had a 55 gal, had it for ten plus years, acquired a 120 and transferred everything over to the 120. Added of course, more sand and more rocks. That was in June. Could not get my nitrates to drop. Was a very deep deep red. Everything looked good though, but went and bought the aquripure nitrate remover. That was September, with in one week of adding that, diatoms. Never had the problem before and have not been able to rid myself of them. Was using tap water, swapped to ro and even added a phosphate remover for good measure, tested phosphates and it was almost a zero. And still have diatoms. Someone suggested it could be in the frozen fish food. But still have the ugly crap even after doing a lot of water changes, sucking out the stuff with sand. Even changed my t5 lights to led lights, nothing has changed.