So I am in the process of building a 630 gallon plywood tank. 7x4x3. and I was wondering about circulation. My 2 ideas so far would be 2 4000gph external pumps hooked up to 2 closed loops (one sucks from the left and puts water back on the right. it turns of and the other comes on doing the opposite, right to left, about every 15 mins) Or buy 2 of the new mp60 powerheads from vortech. Would I get the same flow all over from the two MP60's? or would I need more of them? I know the mp60s have almost double the rated GPH from external pumps and are WAY more energy efficient so they will "pay for themselves after awhile but will I have dead spots? because with the closed loops there would be 4 outputs and inputs on each side.