Hi and welcome!
I will start by saying that sororities are very challenging and they do not always work out. Females can get along one day and suddenly change. You must have a backup tank for each girl that is heated and filtered incase things do not go as planned.
In a sorority, you must plant the tank so heavily that when you look in, you should not be able to see the back of the tank. Leave a strip along the whole front open though so if they do want open swimming space they do not have to crowd one another to get it.
You must keep up on water changes, feed them a high quality diet ( New life spectrum small fish formula and Northfin betta bits are good options), and keep the temperature steady and stable doing this will help keep the girls healthy, as in a group their immune systems are often weakened from stress.
All bettas like heavily planted tanks as it reduces stress for them.
Have a cave like hiding spot for each girl. Be sure there is more than one entrance so they do not get cornered.
Could you please provide a picture of the whole tank? When you say you have a moss ball, does that mean that is all that is in the aquarium ?
I would focus on getting the tank heavily planted and cycled before adding any more fish/ creatures to the tank.
Last edited by Animals15; 08-08-2019 at 01:53 PM.