I have a 150 tank with a 40 sump and a littlegiant 4mdqsc pump.My tank has 2 corner overflows with 1" pvc for plumbing to the sump but it puts so much airbubbles in there that the return pump puts it right back into the tank.I tried to reduce the flow into the sump and it took the air out but if you don't stand over it all the time it over flows my tank.Noise is not a concern,but water on the floor is.any ideas?