Black Skirt Tetra (Gymnocorymbus ternetzi)

The Black Skirt Tetra is a timeless species that has been an aquarium mainstay for generations. It’s quietly dignified good looks, peaceful demeanor, and general hardiness have endeared it to nearly every freshwater aquarist at some point. This is often one of the first tropical species recommended for a newcomer to the fishkeeping hobby, but, perhaps for this reason, it can sometimes be overlooked by those more experienced.

Gymnocorymbus is a small genus with only four species to its name, and, of these, only G. ternetzi is seen with any regularity, with a variety of interesting aquarium strains now available. It originally hails from the sluggish waterways of the rio Paraguay and rio Guapore in the southern portions of Brazil and neighboring parts of Bolivia and Argentina.

As tends to be the case with tetras, this fish occurs in large shoals, with males bickering amongst themselves for the right to breed. The sexes are fairly similar, but females can be told apart for being a bit larger and for having somewhat smaller, less-pointed fins than the males. As you might imagine, this is one of the easier tetras to breed in a home aquarium. The eggs are scattered along the bottom, and, if separated, the fry can be fed on small live foods or finely crushed flake foods.

There are a wide variety of species that make for excellent tankmates, particularly when it comes to groups that naturally occur alongside it in South America—tetras, hatchetfishes, corys and plecos, livebearers, smaller cichlids… as well as rasboras, danios, rainbowfishes, and nearly anything else. However, G. ternetzi does have a bit of a reputation as a fin nipper. This is the sort of disreputable behavior that tends to develop when it is kept in a smaller aquarium, by itself, and with a tempting target. To avoid this as a possible issue, simply keep a large group together so that their energy is directed towards each other.