So about a week ago i was trying to dry out some black diamond blasting media that I did not use in my tank. I spread it out on a tarp and without thinking I went and put my hands in my tank and now have an oily residue on the top of my tank water. This is the reason i decided not to use the black diamond in the first place. I have done repeated water changes and can't get rid of the oil. It doesnt seem to have any ill effects on the fish or plants but does anyone have any suggestions on how to get rid of it?