i had the same thing, Got a 30G tall tank, allglass.. and it has the temperard bottom so i drilled a 2 1/2 inch hole in the top corner of the tank.. Becouse im running a 33G refugium i attached some pictures.. what i did was drill the hole installed the bulkhead and made a overflow box and siliconed it into the tank..
Works very well!
This here is crappy shot of the overflow box i made.. lol installed
and then here is the bulkhead installed and the plumbing!
This is a shot of the sump/refugium
