Are these adult convicts? Tank too small. keep two in a 29 or 30. Convicts are aggressive to one another but have never had one kill another. I have also not had three in a 10 gallon tank?
I presently have about 10 convicts, 4 of which are female (100 gallons). They all get along fine. I have had three litters of @ 150-300 baby convicts, this is when they get real mean but not to one another, especially to the female.
Convicts will eat any tropical food such as flakes, pellets, bloodworms ,tubflex worms, guppies, convict fry, ect.
These fish are tuff. They will live in bad conditions. I feed babies to my sons turtle, some survive in turtle tanK for weeks in water conditions that would be considered horrid for tropical fish.