Dense growth

[RTRJR]

I've had pretty good results from the Eheim SSE, but I admit (thankfully) that I have not had a situation as severe as you describe. My main issue has been the initial adjustment of the unit in the tank, and then knocking it out of alignment while playing around in the tank later. Cover glasses especially get in its way for me.

[Ben Belton]

I find that I have more surface scum when algae is not doing well and/or dying. Not always the case. Hope it is with you.

Ben