Unless your tank is 6 ft or larger, adding a female may be hazardous to her health.
After my group spawned 3 times, I gave the bonded pair to another aquarist. Even though they were only 4" for the female, almost 6" for the male, I kept them in a standard long 125 gal
He put them in a 55 gal, the female was dead within 24 hours.