Hey ATFOWNZ's
Bingo... Tank Size...as USMC mentioned.
Bro... 60 Gallons ? 11 ATF's

..... not to discourage you but they will eventually kill each other. ATF's are skittish when young but being in a small tank will just drive them nutts. Even in my tank they nip at each other. But my advantage is they have space to swim away from eachother and having so many will diverse the attention to others and not just focus on one.
I notice they are more agressive at night also. I noticed soon as the sun sets they get territorial like this is my spot biotch! get away from me...LOL... but in the morning and late afternoon they get together like yea, were ready to go hunting so they group togheter, pretty kool behavior.
In the past I've always read of people failing to keep groups because the end factor was the size of the tank. Dithers are also good to have in the tank. Fish's you don't mind getting their ass kicked or eventually eaten =-( I have bala's also. One Bala is about 9"...hahaha
I'm hoping to upgrade to a tank at least double the size by summer to accomodate the ATF's. My tank is a good holding tank for now. But when they reach close to a foot it's going to be a problem. If you don't have the means to upgrade soon expect to have more casualty.
BTW - Who did you get the ATF's from ?
Good luck bro with your ATF's, post a pix if you can..