Diogenes;3264966; said:Breeding doesn't work like that with serrasalmus species, especially S. rhombeus. It's only been done a handful of times in captivity- in swimming pools, and ponds. Piranhas are not sexually dimorphic which means you can't tell the sex, and S. rhombeus are extremely aggressive towards conspecifics. As far as a I know that don't mate for life either. They don't really pair like cichlids. When dealing with piranhas think "giant killer tetra."
agree, i wouldn't try it unless you have the money to burn. I had one that I thought it's a female but never had the guts to remove the divider, she's too nice to just get killed by the other bigger rhom