Heating and filtration really are all that are truly essential. I would get a lid, too and something for the fish to hide in. A pair of 300W Stealths would heat it. I would aim for 10X filtration. So 4 hydrosponge filters with 300 gph power heads would do.
http://www.jehmco.com/html/hydro-sponge_filters.html . Or you could do a sump with a 1200 gph pump.