I have a 20 gallon long reef tank currently without a sump. I have an extra 10 gallon tank and i want to make that a sump. There's no overflows on my tank so im not really sure what to do. I know that I need the return and the tube carrying water away from the tank hanging off the back. I'm just curious how do you get the water flow out of the tank because it won't drain due to hanging over the back off the tank?