So Serpae Tetras...

[Trey Stamm]

Ever since we added two serpae tetras, they have been very happy fish. However, we noticed that the smaller tetra (not THAT much smaller, maybe like a millimeter or two) started hiding a lot and began having trouble swimming. Many people online assumed that it might just be dying, however it’s been about two weeks and he isnt dead yet.

This afternoon, we checked up on them and noticed his entire tail fine was pretty much gone aside from a small bit, and he was trying to swim but getting carried around by the current, leading him to go under into the small fish house to avoid the current peacefully.

Just now, we got back to our dorm room and saw the other serpae tetra had him cornered and was literally devouring his fins, so we panicked and got him out of there and into a new separate tank.

Is cannibalism normal for tetras???

 

[Colin_T]

Hi and welcome to the forum

All tetras need to be kept in groups of 10 or more because in the wild they naturally occur in groups of thousands, so even 10 in an aquarium is an unnaturally small number for them. In addition to this, serape tetras are renown fin nippers and will attack each other and other fishes in the tank. The smaller of the two tetras is being attacked and bashed because the bigger one is stressed. If you have a large group of them, any aggression is spread out over all the fish in the group and this doesn't happen.

If the tank is cycled and has an established filter, and you want to keep serpae tetras, then buy 8+ more of them so there is a bigger group. Otherwise get rid of them and get something less nippy.

Black widow (black skirt) tetras, Beunos Aires tetras, Blind Cave tetras and Tiger Barbs are all fin nippers too. Avoid these fish (and serpaes) if you want fish with long fins.

 

[Byron]

I concur with Colin. Shoaling fish "expect" to be in a group of their own species, and scientific studies have now proven that when this is not provided the fish become more aggressive than normal. With naturally aggressive species like Serpae Tetras (Hyphessobrycon eques), this is usually deadly for the fish in the tank.

This species, like Tiger Barbs, must have a group of at least 10-12, and those in a 30 gallon tank on their own. In larger tanks, other species may be included with the group of 12-12+, though this has to be carefully thought out as any slow, sedate or long-fin species will inevitably be targeted, eventually if not immediately.