I started with a 20 gallon under the stand 4 years ago. It's increased a bit:
The trash can to the right stores my RO
and is part of the auto-topoff (which also includes the pvc
in the sump that has a float valve, a backup float valve, and holds the 2 heaters. Black switch box controls the pump, every hour for 15 minutes ). There is another one to the right of that for mixing SW
The media bag has reef carbon in it now, I run it every few weeks to polish the water.
Next shelf up has chaeto
Top shelf has some anthelia frags
Just thought I'd show the monster. It's in the laundry room, tank's upstairs. Dolphin external pump takes care of moving the water up, gravity does it on the way down.