Durso question

[E46Twist]

So I got my 125 filled, after 18 hours, and have one SMALL problem. I am using dual overflows on the back glass and I am getting loud suction. The problem is that I could not keep the guard to keep critters out in place if I wanted to install the dursos. My only thought is throttle back the flow until the two 3/4" bulk heads are not being maxed out. BTW pump is at ~1500 gph after head loss, little less after loss from bends. I will upload a pic later to show exactly how I have it set up

 

[E46Twist]

 

[E46Twist]

So the drain on the right is maybe an 1/8th inch higher than the left(go me.) If I put a finger over the inlet or the exit in the sump it back the water up enough to stop it from sucking air. I'd rather not restrict my flow, any ideas?