Join Date: Oct 2010
Location: Victoria, Australia
This is why it's advised to get more than three females. What tends to happen is that the most dominant or aggressive female will continually pick at the weaker females (or female if you only have two), and usually once started, this behaviour tends to escalate.
The problem as already outlined is you have too small a tank, too few females, and not enough cover. So it is not surprising you are having issues with aggression.
You need to either separate the females permanently, or invest in a larger tank (I now recommend a minimum of 15 gallons), increase the number of females to at least five, and drastically increase plant mass.
Even then, there is no guarantee that you will have long-term success. Sororities are a high-risk and high-stress environment, and if you do a search on this forum, you will see that the potential negatives far outweigh any positives. Realistically, a sorority environment offers zero benefits to the fish.
Be careful with your two females. Even if they seem to be cohabitating without issue, it's still very early days yet, and you may find that as they start to settle into their new environment, aggression starts to rear its ugly head.
I also wanted to ask, did you cycle this tank before adding the females? Stressed fish, coupled with deteriorating water quality is a huge trigger for disease, and if the tank is still cycling, you need to be testing your water religiously and doing frequent water changes to ensure that your parameters stay at safe levels. If the tank isn't cycled, you need to be testing your water daily for the next 3-4 weeks.
Finally, if you do add any further females to the sorority I strongly advise quarantining them first, even if they came from the same source as your current females, and even if they appear healthy. Over the years here I've seen so many hobbyists wipe out entire sororities from a simple lack of quarantine. I also say this as someone who personally has lost over 100 fish, because I failed to quarantine new arrivals.