I'm new to the aquarium deal, but I just put a 30g sump in and it was a tight fit just with a sock, skimmer, bubbletrap, refugium, and return in that order. My only regret is that I didn't plan the water height out to match the needs of the skimmer. Trying to decide now if it's worth it to bring down the waterline from 10" to about 7 or 8".