I recently had some tank issues that I think are related to top off water. It was being stored in a clear storage container and started growing algae. Also found the container to be full of dust, floating crap, etc. I assumed a power head would eliminate that possibility but was wrong. After several water changes, I'm having to dose with vinegar because my Alk is 5.75+ (dKH 15-ish) and pH will hit 8.60 if I don't. The situation is getting better, but today I noticed a filmy purple "mold" growing on the sand bed and turning it black. Also creeping onto rock and other things in the tank. Any ideas without a photo? No camera on me right now.