In a space filled with fish shoaling species have no need to shoal as they shoal for protection and in this situation it dosen't help. In a lightly stocked tank shoaling species tend to shoal more readily as it can be useful. Species that must be kept together because they need the company of their own kind are often refered to as 'shoaling' however, they tend not to shoal as they just like the company of their own species and they do not use this company as a defense strategy. They are more likely to be seen in ones or twos rather than in a large shoal.