3 return pumps? That sounds too complicated. Unless you are using some ofor a closed loop, I would reccommend using 2 max. I only use one. Having two running will keep your system circulating incase one fails, but even that is extra plumbing to do and extra pump to clean. I gues two might be reassuring if you are away frequently for more than a couple days. Other than that I would go with one. You shoudl still have additional in tank circulation anyway. To get just the right flow you could look at other pumps also.
I am guessing your pump is going to be submersed?
Check on enheim pumps. Maybe quietone, but Im not sure if they have somethign in between the 3000 and 1200.
The other option would be to use a blowoff to use a larger pump like a mag 7. Split the return line just after the pump. Run one line right back into the
sump and the other up to the tank. but put a valve on each line. Then you can adjust the flow with the valves. The goal woudl be to get the right amount of flow into your tank, but allow enough flow through the blowoff that it does not restrict the pump. though I've seen people do this without the blowoff. I'm not sure what effect that has on different pumps.
