Join Date: Aug 2010
Location: Chevy Chase, MD
It will all depend on the temperament of your girls. I started my sorority about 10 days ago after my 10gal finished cycling and the next morning had to separate one of them, Princesa the CT, because she was overaggressive on the other 3. Given that I had my 2.5G tank in use then, I put a divider on the 10G and isolated her there where she was able to flare at the rest but nothing more.
Three days ago I woke up and Princesa was nowhere to be found on her side of the tank... She had jumped the divider and joined the sorority with ease. She still chases the others around but no more flaring and biting. So I decided it was time for the final member as my filtration and cleaning schedule would allow up to 5 Female Bettas on the tank so I went and got a nice silver and violet VT, Vio and had to watch over the restatement of leadership on the tank. But everything was over in a couple of hours and now the five girls live together in harmony. There is chasing and the occasional drive-thru flaring but that is the end of the aggresion between them.
So, yes you can have four girls on that tank as long as you take the time to get them to know each other and watch for excessive aggression.
Chori - Female VT
Princesa - Female CT
Vio - Female VT