I agree with Gizmo. Female bettas need a larger tank with lots of cover, 10 gallons is what I'd say is the minimum. I have a densely planted filtered 20 gallon with 10 regular females and 2 giants in it as well and they're happy! They can all live together and they make for a really beautiful tank but they do need to be set up properly, with a minimum of 4 girls - with 3 females two tend to gang up on one, and they can be just as aggressive as males and kill one another!
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