Is it common for Cardinal Tetras to harass and nip each other? I was at an aquarium store, intending to get them after adjusting my water to their needs, when I saw this behavior. There were about 15 Cardinals in the aquarium and all of them were darting at each other and nipping at each other's bodies pretty constantly. They were definitely making contact too, they weren't just lunging and veering off. All of them were doing this. I must have watched them for at least 10 minutes, and nipping was the primary activity, they were all staying in half of the tank by each other nipping and lunging away. I was under the impression that these were very peaceful fish, but now I'm wondering about them. They were really washed out (they barely showed their red colors at all). Could they have been doing it due to some environmental factor, or is nipping at each like this other normal behavior for them?
I have a couple other types of Tetras - Black Neons and Gold Tetras - and I know that there will be a hierarchy within the school. But while I've seen my Gold Tetras chase each other they've never actually nipped each other like this. And while I've seen my Black Neons display to each other, I've never seen them actually make contact either. So I think what the Cardinals were doing, actually nipping each other's bodies, was on another level than what I've seen from these peaceful Tetra types.
I have a couple other types of Tetras - Black Neons and Gold Tetras - and I know that there will be a hierarchy within the school. But while I've seen my Gold Tetras chase each other they've never actually nipped each other like this. And while I've seen my Black Neons display to each other, I've never seen them actually make contact either. So I think what the Cardinals were doing, actually nipping each other's bodies, was on another level than what I've seen from these peaceful Tetra types.