Honestly, when I got bored of my frst 46 gallon freshwater tank....I want big for a 72 gallon freshwater...bought all fish imaginable (even stingrays).....then went to fish only with live rock....to reef tank.
If I was you I would change that tank in to a FOWLR, and have Lionfish, moray eels, smallish angelfish/triggers
People say live rock is exspensive...is true however just by dead......nothing wrong with dead and actually it is better in the long run as numerous things follow:
-No worry of hitchhikers (aiptasi anemones big big problem)
-Cost efficent
-In a few months times the rocks became "live"
IMO you could probably set up the FOWDR for under $100- $200 easy with out fish.
Any questions on the possibility of changing your tank into marine let me know, or post it up in the marine section where you will be happily guided.
Happy New Year Everybody