Sorry for the late reply. I am not getting notifications about new posts for some reason. That said, you’d want about 2” of clearance to remove the lid. Removing the cup only requires about an inch. You’d be better off with the Deluxe 250 though. I wouldn’t recommend a 300 sized skimmer for anything under a 500 gallon main display with a truly heavy fish load. A heavy load is 1/2” of fish per display gallon.