Can anyone help with this? Pond is well over 20 years old , last year i started getting this green stuff on top of the water. When it rains its all gone, a few hours later it gets like a grayish dusting over it and by the end of the day its all green again? Where the bubbles are from the airator there is never any of it. Anyway to get rid of this and what is it . It doesn't look like typical algae that you can just pull out. Looks like a coating ot op of the water . It looks horrible. Has been going on since beginning of May.