Scum on surface 3 days after putting substrate in
Last Sunday I filled my 75 gallon with water for the first time. I'm using Flourite black sand as the substrate, which I rinsed very well. There really isn't much of anything in the water column, but on the surface there's this thin film of scummy stuff. Is this normal for a newly filled tank? I've tried 'knocking it down' into the water, with minimal success. Will it go away on it's own, or is there some way I can get rid of it? Any opinions would be greatly appreciated!