I would add another three spot gourami variant pair(the gold gourami, as well as the opaline and I think blue gourami, are all three spot gourami variants), or a pearl gourami pair. paradise fish are like bettas, some don't like tankmates, while others do. In my expiereince, three spot gouramies enjoy killing(well, maybe not enjoy, but they kill them either way) drawf gouramies, and would probably do the same to similar gouramies. Snakeskin gouramies may work, depending on the front to back measurement of the tank (I'm pretty sure a 60g is 12" front to back, so this species is probably a no-no, as they get to 9-10 inches).