Hi, just don't know what these are, its all over the tank floor. Clear them everyday, and is still appearing. I was getting a 2ft tank ready for nearly 2mths for use as pleco grow out tank, but have been getting this light and sand-like particle every day. Its brown most of the time, but occasionally its greenish. Is it still safe to put my pleco fry in there? These fry are still in the breeder box now.