I had only two Veiltail betta females (Ariel & Emerald) that did great together in a 1.5 gallon tank. Neither showed aggression towards each other. Unfortunately I am leaving for Ohio in a few weeks so I recently bought a 10 gallon tank that has a heater and thermometer and also LED lights when I get the missing part and I also purchased 2 more fish to have a sorority so less aggression (or so I thought). I now have three Veiltail females Ruby (red/white Veiltail), Ariel (blue/green), Emerald (blue/green), and one Crowntail: Sapphire (blue but looks blue/green in picture. After watching them for 30 minutes I noticed that Ruby was being aggressive and chasing and nibbling the other veiltails and crowntail around the tank. I put 6 silk plants in the tank so they have plenty of room to hide. I got told this is normal for betta females to be aggressive for the first day or two then calm down. I am just making sure because I am worried.
F.Y.I. Emerald is the betta hiding in the plant that you can't see her completely.