Hey, you should buy like 3-4 convict cichlids, there awesome fish, they come in two colors, white/pink, and black/common. they breed like crazy!! they are very hardy with the water conditions too!! they can handle high nitrates,. you can decorate there tank with slate rocks, and they usually lay there eggs on them!
If you want a Semi-Agressive tank you could do a few Angel Fish? Or if you want a Agressive tank you could do a pair of convicts? Your choice! I peronally am new to convict cichlid keeping and i Love every minute of it!! But Angels are cool fish too, Especially if your tank is taller than it is wide?
-Patrick