72 bowfront built in overflow
According to Oceanics site, the two holes on the bottom are for drainage and for bringing the water back in. Can someone tell me how the previous owner had this set up? Is it two drainage flows on the bottom while the pump (from the wet dry) puts water back in? The pipe running up from one drain baffles me, since it is higher than the water could flow into from the overflow. The water from the sump can run through that pump on the bottom and back to the tank (I assume.) I hope the pictures can help you all understand what I am saying.
Also the other hole is flush with the bottom of the overflow.