I will be adding a sump to a 28g JBJ nano and have a few ideas to throw out. The tank is all ready up and running so I do not want to take a chance to drill the back for the overflow. I will be using a Eshopps-300 for the HOB overflow. Jere is a photo, I swiped from another site, of the back of the tank showing the configuration of the baffles. If I remove the filter box from the center partition, is there any reason why I can`t use that area as the internal box of the overflow. The return line will be split and go into the outer partitions where the return pumps are. This way, the wave maker can still be utilized. The return water flow will probably be adjusted by a ball value, and maybe a couple of holes be drilled into the back wall of the tank by the return jets to assure no overflows. Any input will be appreciated.