Capacity of my tank

Question
Hi Lynda,
    A friend of mine just gave me his tank and I have the feeling that it might be
overcrowded. It's 55 gallons tank with plenty of hidden areas (flower pots, rocks,
sea shells). I have 3 full-grown male convicts, 3 full-grown females, two younger
undetermined gender, and one developing young. The aquarium also contains 2
electric yellow cichlids and one catfish (which is 6 to 8 inches). I wouldn't mind
adding one more specie for variety's sake, but am quite certain that this is full-
capacity. So is it? If yes, how many would you keep in order to add another specie
(An aquarium store is willing to take a few)? What other specie would you
recommend?

Thanks Lynda,

Vincent

Answer
Hello,
I would not recommend any other fish with convicts.  Sooner or later your convicts will breed with the females, and they are very aggressive parents.   They are good parents, but may kill, or hurt any fish that goes near their fry.  You tank is overstocked, you cannot add any other fish.   If you decide to keep your convicts, I would not add any other fish with them.  If you go with electric yellow cichlids, and bring back the convicts then I could tell you what fish to buy, but I must know the gender of the other two fish you have in your tank.  I cannot help you if I don't know.   Make sure your water has no ammonia, nitrites are zero, and nitrates are low.  When starting a new tank, this is very important.
Let me know what you decide.
Lynda