Do you prefer to have a water pump inside or outside a tank?

[subman]

I've always run internal but thats always been because my setup wouldn't allow it any other way. I see what Grizz is saying but in my case I think the heat is a benefit as it just means my heaters run a little less. When I was running MH I really could have used external pumps.

[AquaPin]

My tank is in the basement, so the little bit of heat the internal pump generates is fine with me. Plus less hassle, the pump has a PVC going to a hose that returns the water to the tank.