These are just about the nippiest tetras in the hobby. They need to be kept in a larger group (12+) in the hope they'll keep their nipping to their own species, though that doesn't always work. Years ago I bought 6 serpaes and next day every other fish in the tank had bits missing. They went back.
There is a similar looking alternative, red phantom tetras
Formerly Hyphessobrycon sweglesi. The red phantom tetra, Megalamphodus sweglesi, is a small characid endemic to the upper and middle Río Orinoco watershed in Colombia and Venezuela. It apparently favours minor tributaries, oxbows and flooded forests, and in Venezuela is often found in morichals...
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