Pump to tank size

[Aquattro]

It looks like a lot of people here are trying to supply the tank water movement with their return pump. In fact, the slower the flow thru the sump, the more time the skimmer/heater/etc have to act on the water. You don't want to create 10x your tank volume goig thru your sump!
For intank circulation, rely more on powerheads or closed loop setups. This lets you customize your flow as your corals grow. I recall when I first setup a tank and tried to get my MAG 12 to output in several locations, and in the end each output had almost no noticealbe flow. After plumbing losses, each output maybe had 300gph flow, which is equivelent to a regular powerhead. And unless you have a smaller tank with a huge pump, that may not supply enough flow to keep detritus supended of to provide optimum growth for the corals.
As to the heat comment, I don't notice any heat generated from my 2 streams, 1 powerhead or MAG 12 submerged pump. But my tank is a larger volume, so it might be aconcern on smaller tanks.
Just something to think about...