y does my female betta stay at t..

Brief：
i have two females and two males i bought two tanks and i serperated the bettas out putting female and male together and i noticed one of the females .. 

i have two females and two males i bought two tanks and i serperated the bettas out putting female and male together and i noticed one of the females were havinng trouble wit a male she was at the bottom of the tank breathing hard and wouldnt eat or move she was missing some scales and a fin so i seperated them but the other two were doing fine

Take her out of his tank now! He will kill her if she remains with him.

Unless you have a very large tank (over 20 gallons) and have it well planted with plenty of places for her to hide you cannot keep her with the male.

Males accept females only for a short time. Once his bubble nest is built and she is full of eggs, they mate. As soon as they are finished mating, the female needs to be removed. The male will raise the fry himself.

Good luck! maybe that is where she feels comfortable and safe for the first 2-3 weeks I had my Oscar he would hide behind a castle in the tank but now he never goes there he just swims around is it possible that they wherer fighting? how is she doing now? sonds like a disease It is quite possible that she had a heart attack. ya theyre fighting, bettas dont get together at ALL unless its to mate so they shouldnt even be in the same tank together

even if it is male and female SEPERATE THE MALES AND FEMALES NOW!! The males will kill the females. The reason your female is at the bottom of the tank is that it is fearing for its life. The only time to ever have male and female betas together is about five times a year when you notice very large amounts of bubbles (larvae) floating on top of his tank. But yes your females will definetly die if you leave them in there. As beautiful as they are, they are also twisted little fish. Ive got a few myself. NOW SAVE YOUR FISH! some times males attack female 4 no reason! try another male?

once 1 of my males killed the female but iv only ever had problems with that male! all my others that iv had were fine with the females!

ur male betta is just a bully!! It sounds like the male was trying to drive her out of his territory. Which in a tank or bowl tends to be fatal. It is rare that a male will let any female live with him long term. At best they'll mate, produce 100s of offspring, then he'll try to kill her. Even among females they will tend to fight. Being able to see the males tends to increase fighting.

PS- Keep in mind bettas are not people. They don't get lonely. Their only type of social interaction is aggression, and mating. Even your females will never be friends.