I currently have a 55 gallon tank with 4 jd's , 2 firemouths, 1 green terror, and a gibbicepps pleco. I will be getting rid of 2 of the male jack dempsey's as they are both fighting with my nicest colored male. He is almost 5 inches, while the rest of the fish left only average about 3 inches. Can i add something new to the tank, or will i overcrowd it? If i can add a fish, any suggestions? thanks