That would sure be one cool "den", though.
A shop I worked at once upon a time had a similar,1800 gal., shark tank with a black tip and nurse shark. A large mound of live rock in the center was built to create a place where the damsels, tangs, and angels who shared the tank could take refuge. Seems like I remember there being condy anemones, also. Quite the conversation piece, we would get groups of school kids coming in to study the sharks, everyday at 4:00 there would be a feeding demonstration, articles written in the local paper, etc. This man's actual tank looks nicer, though. The shop's tank had "portholes" you would look through to see the sharks.