06-06-2010, 02:29 PM
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Agree. Perhaps I could explain a bit about the difference between schooling and shoaling, since tetras are strictly speaking shoaling rather than schooling fish.
Marine fish (some species) school which means they move in large groups to avoid predation and feed. Freshwater fish (those that need to be in groups) however tend to shoal rather than school, which means they are less stressed in groups of their own species though few actually move (swim) about regularly as a tight group. They shoal for protection and some species have a sort of social order within the group. Observations in the wild and in aquaria have shown that the environment (plants, wood, rocks, etc) can influence the size and behaviour within the shoal.
There are a few tetras that shoal in group formation quite a bit; the rummynose tetra is probably the best, and cardinal tetras also do this. But they eat individually, and the fish within the group will often go off on their own, or in smaller groups of 2, 3, 4 etc. Some of the tetras have elaborate display and pre-spawning rituals, and these are only observed if the fish is in a shoal or group.