Tank with false wall.

[seashells]

We picked up a used 55 g acrylic tank. The back wall has an over flow area built in but not drilled. Seems to have been used like an intank sump. Plumbed with slots on the top for intake & and a spot for a return pump. Anyone have any experiance with this type of tank? I think it would work like a prefilter...but you would also be able to hide heater etc. there. Any other ideas?