Work sucks today..so I've been looking at fish porn

[Doug]

I think the 100g Rubbermaids are the coolest things for sumps ever. I had one back in the day. My friend now runs it on his 180g. Sealing an overflow hole is easily done. Just silicone a piece of 3/8th. {minimum} glass over the hole of if the sump was elevated a bit, one could put a drain valve on it.

Or I have also made stand pipes with caps on them and either pvc glue it into the hole, {permanant method}, or silicone it in, {can be removed with a bit of twisting or if the exit side is valved or something you could just use plumbing tape on it. Mind you most of these methods I used with the overflow divider still remaining.

I have done the complete removal and siliconed glass over the drilled holes though. Still like the 100g Rubbermaid better. Easily drilled, has a drain plug if needed, excellent shape to work in and best of all, unbreakable. Also a nice shape to hand a central halide over if one wished to do frags or pehaps algae of some type.