I'm just about done setting up my 40 Breeder, and the drain is doing strange things. Tank info; 1" drain with Durso, 3/4" return on a Quiet One 2200 (little less than 600 GPH before head loss) Drilled in the bottom with a DIY overflow box. The water in the overflow box is nice and stable, however if I open the gate valve on the drain and return all the way up, the water entering the sump has so much air in it that it looks like it is violently boiling. At the moment, I have both the drain and the return closed about 25% and now it is just a small fizzing, but I'd really like to be able to turn the flow all the way up. The only thing I suspect is back pressure. The drain pipe is about 1" under the water line in the sump. Is that okay or should it be above the water line? What else can anyone think of? Thanks!