Maroons are extreemlty agresive and territorial, i wouldnt put another fish, ofcourse u can put gobies, blennies or something like chromis, there are lots of options but maroons also get too big, i mean i wouldnt add any fish to this tank and make a maroon tank, i ld pay attention to my corals and clams more, also u can add more anemones, some anemone crabs and some anemone shrimps and sexy shrimps, and that hermit which has anemones on his shell, i would do like that, i think could be cool, i wouldnt put swimmer fish, but a very colourful and rare goby could be cool too