i used to have a sump that is typically a water trough for cows, you know the kind from rubbermaid. i painted the inside white with that paint. i let it cure in the sun for a week and ran it for a couple of years without a problem. i ran extra carbon the first month just to be sure. coralline grew on it as if it were plastic. it kinda bonds with the plastic.Phyl said:Can it be used IN-tank, that you know of, Rich?