I have the 60g (24x24x24) and it came with the center overflow, two pre drilled holes in the back (drain and return). I came straight out from the drain, 'T' then down to the sump, left the top of the 'T' open for air, the return is just using a Marineland 1800 from the sump to the tank. I have had it this way since Nov 09, all is well and good, I love the cube.