Mine has only been very minimal spots on the pool floor. Looks like dirt/dust to me, but pool repair guys have both said it was mustard algae.

Sounds like it can get out of control though.

I don't use my pool vac at all since getting the PoolBuster Max CG. That way, I feel better, knowing it isn't going through the pump or filter at all. With the micro fine filter bag on it, it is amazing what it sucks up. Love that vacuum!

John