Which best kept in a shoal

[DeepSouth]

Which marine fish, that are commonly held, should be kept in groups of 4 or more.

 

[Hitman]

Chromis, some triggers, clowns, some tangs in odd numbers, it really depends on tank size what you can get away with. A long and wide tank with plenty of swimming room will allow you to do more with certain fish then a tall skinny tank.