overskimmed?

[Bax]

How about experimenting with a PVC coupling & a piece of pipe on that water level tube and see what response you get?

 

[miwoodar]

Cleaning the neck a couple times a week is super key. Mine will only pull gunk a couple of days in a row...after that it is nothing more than a fancy bubbly thing until I clean it again.

I agree with the 24/7 group. Consistant water parameters are required for success in any system. Be it for skimmate production or simply for aeration reasons I wouldn't turn it off.