I've never tried this, but it was recommended to me once on this site (but it was awhile ago, so i'm sure there have been good and bad stories about people trying this since then) But with a ten gallon tank, you could possibly get 3 female bettas as long as you have plenty of places for them to hide and so no individual one really gets picked on. I was told that there will be one dominant one, but the other two will share the picking on, so it will be ok divided like that. I could be totally off my nut here or ten gallons could be too small for this idea.... but just a thought. Feel free anyone to set me straight