I think your male may not be big enough - compounded by the cramped quarters and he being the introduced one. Having another pair to see and scrap w/ through the glass will help. But what I have seen over the years is that female Festaes will abuse their males, if they can't hold their own. If he isn't big enough to fight back, the end is inevitable. And Festaes are very sensitive fish in that they have a hard time recovering once their feelings are hurt and can even totally shut down. They do not do well being picked on like a convict, for example. I know it's tough b/c they grow so slow, but I would beef him up and then put them back together, introducing her to his tank. BTW, I've found festaes grow way faster as a dominant fish in a smaller tank than as a weary fish in a huge tank.