I have A fairly big one that that I've had for about 2,5 years and it's a nightmare.
I've tried doing a group but it just ended up with "him" taking the eyes out of the newcomers.
He just recently killed an armatus that was about the same size as him (30cm..ish) and it had a tendency to bully my ATF as well.
Keep a close eye on them for any hints of a terror like mine.