Bettas

[IONMEL]

i know male bettas are aggressive, are females aggressive as well

 

[aly_starh]

Female bettas are aggressive, but not as much as male bettas.

A group of female bettas are called a sorority. This consists of atleast 6 females.
If you do want to keep a female, but not 6, then only keep one.

You will be able to keep 6 in 10G with a good filter and heater.
There will be initial aggression, buy this is just them sorting out whos boss.

Hope that helps