A 210 gallon would be wonderful as a FOWLR. I would like to down the road do that to about a 300g. With larger tanks like said before you can put in Angels and also like said before the Wrasses. I had a Lunar or Moon Wrasse in my 125g before I decided that I wanted inverts in my tank. With a 300g, NOT AT ALL KNOCKING A MONSTER LIKE A 210, but with the 300 you get 2 extra feet of swim room, also if you have the room. But back to the point, having a more aggressive tank like that can open up a whole different realm check out the aggressive forum for some ideas of Angels, Groupers, Wrasses and the like.
Good Luck and sorry about the rambling.