Imagine you have a first import and don’t even realize it! That’s what’s happening to us right now with a tetra. We received some very beautiful, large Hemigrammus coeruleus from Colombia. At least, that’s what we thought. By chance, Peter and Martin Hoffmann, from whom we often and gladly receive rare tetra offspring, needed a few H. coeruleus. Some time later, they asked where they came from. When we answered (Colombia), they said: Flavio is right again: they are Hyphessobrycon acaciae. Flavio refers to Flavio Lima, the tetra specialist from Brazil (Universidade Estadual de Campinas). The two had asked him about the identification of the fish, as they had noticed some differences from the usual coeruleus.
With the naked eye, it is almost impossible to tell the difference between freshly imported Hemigrammus coeruleus and Hyphessobrycon acaciae, even though they are classified in two different genera. Technically speaking, the only difference between the genera Hemigrammus and Hyphessobrycon is that the base of the tail fin is unscaled in Hyphessobrycon, but scaled in Hemigrammus. This is not noticeable in living fish underwater. It has been known for decades that four of the main groups of South American small characins (the genus pairs Hemigrammus/Hyphessobrycon and Moenkhausia/Astyanax) are artificially classified and do not represent a natural relationship. But the work involved is very lengthy and complex, and it will certainly take quite some time before we really understand it.
For us, this means that we will now always have to carry out a special examination when Hemigrammus coeruleus from Colombia arrive. Using a powerful magnifying glass, we have to check the tail fin for the characteristic scaling, as the subtle differences in coloration are not visible in freshly imported animals that have not yet acclimatized. In terms of general care requirements, the two species do not differ. Both species are peaceful schooling fish that can reach a total length of 5-6 cm (including the tail fin). For H. coeruleus, see here: https://www.aquariumglaser.de/en/09-characoids-tetra-relationship/hemigrammus-coeruleus-4/
Text & photos: Frank Schäfer
