A 210 would be great.
I had one that grew to 10" and he was a hateful SOB...he'd bite, spit water and bully other fish just beacause he could. Then, the next day, he'd be the sweetest little fish.
mihifisi...a clean up crew is gonna be tough to keep. Mine killed and ate 5 Red Starry Hermits, that were bigger than golf balls...one was almost baseball size. I called him the Hermit Assassin.
A deep sand bed is required to house them, as they'll sleep in the sand and they'll also hide there when they feel threatened.
Mine was known to pick up pieces of live rock that were almost as big as him and carry them around the tank...so, make sure your aquascaping is in order.