With a 55 gallon tank I'd go with only about 3 or if you want a lil more then do 5 where you have one male and the rest females.But if you breed them and they pair off then you may be ok with just all them females instead of males where they would kill anything in sight.But if you want just take the breeding pair out and set up a 20gallon for breeding and follow the breeding of the fish and once that happens take out the male or female that is or keep both in if you want but,I'd take that pair out and put them back in the bigger tank and your fry will be fine...
