many people buy complete 75/90 gal systems with 20gal High glass tanks as sumps.
I've got a 29gal tank under my 75gal
it holds my filter sock, ASM Mini G skimmer, internal 24w UV sterilizer, 250w Heater, a media bag full of rubble rock, and my 1050gph return pump, as well as about 10-20lbs of...