Personally I would suggest that you add to your tank a few Amano Shrimp. They clean up quite a bit of algae, they are peaceful, fun to watch, and they produce a very small biolode for their size (up to 5cm). Then, as far as a centerpiece fish, a pair of gourami would be nice, or a few rainbow fish, you could even go with a pair of german blue ram, they are very cool fish.