For some reason in emails, in person (weird huh?) and on the forums lately I have been seeing and recieving alot of questions about mixing female bettas together in the same tank. So.. here is everything I've learned about mixing female bettas.
For those who dont know, I have a 10 gallon filtered, heated tank with 6 female bettas (rhonda, gina, silver, princess, smurfette, and little girl) all living quite happily. I have had (including these 6) a total of 9 female bettas, in a few different combinations. I have kept them alone, together, and in a 10 gallon tank at one time I had a powder blue dwarf gourami, and 2 females, and later I had 1 female in a community tank with tetras, cory cats and a 2nd powder blue. The females fared well in all combinations, however the biggest fish in both cases was 2 different dwarf gouramis, and the bettas got picked on :( I think I would only add female bettas to a community tank with docile fish.
Since keeping a female betta species tank, I have only really had 1 issue with agression. we called her "bi##h" for obvious reasons :) she was king dog of the tank and really chased and bullied the other female bettas. At this point there were a total of 4 bettas. She never really attacked the other bettas, but would chase them away from food, and wherever she decided to hang out. Its important to note that it was explained to me early on that female bettas will be a little unsettled with each other for a week or two until the pecking order is established. What im talking about here when I saw bullying is anything beyond that, when ONE single betta stands out as a bully after a week or two. All that needed to be done at this point was to remove the agressor to another tank (had a 2nd 10 gal set up by coincidence). She spent a week by herself in the tank, then once the other bettas had a chance to settle in to their new home, I readded her, and that was the last trouble she gave me until she performed her double 2 1/2 turn double back flip with a twist and a smack out the filter hole in the back of the lid.
I have a few plants in the tank, as well as a make shift tupperware bowl-cave. At present about 10 fake plants line the back of the tank, and one or two small ones in the foreground really give the bettas a chance to be on their own and keep to themselves if they feel the need, but most of the time all 6 are swimming up front together, active as can be. they even eat together with no agression issues what-so-ever.
so there, everything you wanted to know about mixing female bettas but were too afraid to ask :)