It is true that if you have 2 or better 3 females , one the most dominant will turn male. You need to introduce them at the same time so there is less aggression since no fish is established yet. I had a female too before and tried to pair it up twice with another one but was unsuccessful. Even the new females I tried were bigger than the one I had, they were beaten up almost to death within an hour. I stopped trying and just got true pair. From other peoples experience I found on other forums they had the same results as me unfortunately.