First cichclids

If you are doing african, just make sure that you can get the water to the high hardness and pH that they need. Some people, like me, have water that is basically already there, but others have softer and more acidic water that wont work for africans. If you are going to go with africans in a large tank, I have always liked Pseudotropheus saulosi. The males are blue with black barring and the females are bright yellow. You get two beautiful colors in one tank without having to worry about mixing species. I have never kept them, however, so I can not give too much info on their care. Good luck!

I'd recommend African mbuna. They generally stay much smaller than SA or CA cichlids, and overstocking is encouraged to cut down on tank aggression (though you need to upgrade the filtration and water change schedule to accommodate).

Since 55 is not a terribly large amount of space for a generally aggressive type of fish, I'd recommend some of the more peaceful species. Yellow labs, [FONT=Arial, Helvetica]fuelleborni[/FONT], socolofi, acei, rustys...

I would go with something that works with your water. If it is alkaline and hard, then African cichlids are a good start. The suggested species were good.

If it is softer and acidic or turn acidic, then South American may be a better option. The hardier acaras are often a good start. If you want a planted tank with smaller fish, then the captive bred apistos are realatively hardy. Also angelfish are a good option.

Central Americans tend to like moderate(a little bit alkaline and hard) conditions. I think Firemouths and Nics are some of the best options. Convicts will take over the tank and overpopulate it. However some of their more peaceful relatives may be worth a look.