Join Date: Jun 2010
Location: Northern Virginia
I think she'd do well with a school of eight pygmy cories in the ten. They're very small, so you can fit more in than other species of cory catfish or minnows, for that matter. Just make sure that you add them slowly so that your bacterial colony is not overwhelmed and has time to grow as you stock your tank.
Sororities are risky--if you don't have the means to house every girl you put in the tank separately in case things don't work out, then it's not a good idea. Sometimes you get a group of females that simply can't adapt to a social situation. Bettas are generally solitary fish, so they don't necessarily do well when we impose an enclosed social environment on them, so there is always a risk of injury or death.
You can take certain precautions to minimize this risk, such as getting a large quantity of females in order to disperse the aggression (so the same betta isn't getting beaten up all the time), filling the tank to the brim with plants and decor (VERY important), doing a proper fishless cycle on the tank at the beginning so all the females can be added at once, and rearranging the decor often to break up territories, especially when a new fish is added. You should definitely research multiple sources on how to establish and maintain a sorority before you go further.
A community tank, on the other hand, would be easier to establish and you wouldn't constantly be worrying and counting your bettas to make sure that one hasn't decided to kill another that day.
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