Blasting Sand created Oil Slick Help!
So a couple weeks ago I switched my pea gravel to black blasting sand. I had thought I washed the sand out fairly well, but I was wrong. When I carefully added the sand, there was an apparent oil slick formed on the surface. So I siphoned off the surface layer to remove all the oil. O day later, the oil slick is back. This has gone on for about 2 weeks maybe of the back and forth between siphoning and and the oil slick. I don't know where it keeps coming from!! Is this just a game I will have to keep up until it finally subsides? The good news is, none of my fish seems to be effected by it, however I only had hardy fish in there (red eye tetras and peppered corys). My biggest fear is not having this issue solved by the time I get angels or less hardy fish and having it effect them. Attached is a photo. Any help would be grateful