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
At least two colour forms have been traded, one of which is more intensely-coloured and has been referred to as H. sweglesi 'red' or 'rubra'. The bright red pigmentation is retained in long-term captive specimens, suggesting that it is not considered to be an artefact of diet, but we suspect it...
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