I feel it's tough giving suggestions, as choosing fish js so subjective. I would check out sites like bluezoo, vivid aquariums and live aquaria.com. Lots of pictures and info on various fish, suggested tanks sizes and even compatability charts. Come up with what you like and run it by the crowd here. The smaller tank will limit your choices, but there is still lots out there. Cardinals and/or a Pygmy angel would be my suggestion. Most angels, tangs or triggers will need a larger tank.