If you don't want Cons for aggro reasons maybe you could try a pair of Firemouths, remember its a good idea to buy 1 male and 2 or 3 f/males and find a home for the other guys when a pair form.
Other candidates for a 33G are:
Any of the Apistos, Rams, Kribensis, Keyholes, Mary's cichlid, blua...