I can not for the life of me keep Pictus in groups for any amount of time, I’ve currently got a single specimen doing great, however the group I had him in just seemed to die off or I would wake up to pieces of them, god only knows but I’m reluctant to try keeping more, which I would love.
I've started with 27 pictus in a 240 (US) gal 8x2x2ft (then +6 more in a few years). They do fight it out a lot, especially after they sexually mature, and maintain a hierarchy, at times pretty viciously, which is a source of stress, of course, and probably the cause of an occasional premature death.
I've had problems with tank mate predation and disease - the two primary causes of deaths - and as of now probably down to about 15, that is 5 years later.