I think it was in the tank for a few hours because I woke up to it. Threw in some Phosban (Is that GAC?) and did a 20 percent water change. I will do another 20 percent tomorrow. I unfortunately live in an apartment and cant keep more than 10 gallons of water at a time on hand.How long was it on the tank?
Throw in GAC if you haven't. Could be grease/oil from the bearings.
Did you do a large water change?