I am using a Mag drive MD7 on my system, I am not sure if I calculated it properly for my system, I have a 100 gallon sump, three 100 gallon growbeds, and 360 gallon fish tank. the height of my fish tank is 40". The flow to the growbeds are good, but the flow of water going back to my fish tank is very little. My setup is based on a CHOP2 system. Water from my fish tank returns to the sump by gravity. The pump at the sump feeds the growbeds and the leftover goes back to the fish tank. I am not sure if I should buy a bigger gph pump or adding another pump that can pump the water from the sump to my fish tank to increase the flow of water coming out by gravity