sump size for 220g tank

[Milad]

go big, even if you can get it bigger than your display. I have a 70g under my 180g and im still drawing out plans to build a shed and have a massive 300g or something setup for my sump. ive ran out of space and i cant even put my reactor in with my 70 but then again i got tons of live rock so its filling up my sump.