mine appear to dislike bright light.
1 24w t5ho when its on they are dispersed when night/blue led
is on they seem to group up more.
light on they tend to stay in lower 1/3 of the tank near the plants when led
on they use upper portion more & 5-7 will group together but I know what you mean about all the posts/reviews which claim they have a pecking order etc i havnt seen that either,except a small amount between the smaller fish.
the last 3 i got were what was left @ LFS
& they were constantly @ each other in the store, got them home where they had more space & it stoppped in 24hrs,those 3 are the largest i have.
seems the larger few could eat 24/7 if i go near the tank they come running..lol
possible both our shoal's just need to grow-up..lol
my larger barb's ignore the smaller 1's & vice-versa so i doubt you getting some more mature fish would change the pattern.
luckly wife has a 5g betta tank so the 5 remaining cory's are in there now but with a betta & 6 neons & 3 myst snails,that tank is a lil crowded now& needs more looking after but everyone in there is getting aloong ok