I have a Mag 9.5 return pump for my system, and with the new tank with built in return ports I think the pump just isn't enough anymore. If I did the headloss calculations correctly "used RC Calculator" I have about 530gph coming out of the ports. However it does not feel like it is even that much. I have 1 3/4 pvc pipe from the pump the T's off into 2 3/4 pvc pipes that then have a 90deg bend up to the 2 returns with 2 outputs on each side. Total hieght is about 5'. I am not trying to generate most of my flow in the tank from the return pump but I just don't think that the flow I am getting is enough to circulate the water.