my experience with chromis has not been great...
started with ~7
lost one, then another... finally i ended up with 2 pairs...
1 dominant pair which quickly outgrew the other pair...
then the dominant pair took out the smaller pair...
the the remaining pair had a domestic dispute...
thus i have 1 guy remaining.
and NO, 2 in a 55 is still just a pair, you could put them in a goldfish bowl and theyd still be nothing but a pair!
personally i consider ~5 to be a school, no i didnt make that number up... i just trust Brad!