At the store i worked at we ran a 1" i.d stand pipe with a 2" i.d sleeve over it with slots cut at bottom and top. That way it could flow water up through between the 2 pipes. Just cut the outer one an inch or so taller.
This seems like a good idea too but it wouldn't really work if you had a hole cut in the back of the tank for the water to drain. I've seen this concept with built in overflows though where there is another piece of acrylic blocking the slots where the water would flow in. I think the set up I saw was more so that the floating food wouldn't get sucked up since it was an arrowana tank.
