Black skirt tetra

Geographic Origin and Biotope: South America (Paraguay, Guaporè, Paranà Basin). Native to small slow rivers and wetlands covered by the forest canopy, in often amber waters but with less extreme parameters compared to the Amazon basin.

Taxonomy and Morphology: Black Skirt Tetra (Black Widow Tetra). Characin with a very high, rhomboidal and laterally compressed body, characterized by a very extensive, black and draped anal fin that resembles the hem of a skirt. Reaches a good 7-8 cm (3 inches) in size.

Social Behavior: Obligate gregarious (minimum 6-8 specimens, ideal 10+). Extremely lively and fast. Within the school they establish a rigid hierarchy constantly chasing each other. If kept in too small numbers, they become thugs and bite the fins of other fish.

Coloration and Sexual Dimorphism: Silvery gray body, crossed vertically by two distinct anterior black bands. The posterior half and the large anal fin are black (intense in juveniles, fading to smoke gray in older fish). Females are noticeably more corpulent and round.

Aquarium Setup: Due to their extreme liveliness and the size they reach, they require aquariums at least 80-100 cm (32-40 inches) long. Setup with central swimming space and dense peripheral vegetation. Adding woods to release tannins wonderfully darkens their livery.

Diet and Feeding: Voracious omnivore and not at all demanding. In nature they prey on worms, insects and small crustaceans. In the aquarium they instantly devour any flake food or floating micro-granules. They enormously appreciate freeze-dried and frozen bloodworms, daphnia or brine shrimp.

Water Quality: Extremely robust ("bulletproof"). Tolerates a very wide chemical range, making it perfect for the basic community aquarium: pH 6.0-7.5, GH from 3 to 15, and temperatures of 22-26°C (71-79°F). Clean water prevents color fading.

Compatibility and Tankmates: Excellent with Corydoras, Ancistrus and fast Danios. TO BE AVOIDED the combination with slow fish with veil fins (Bettas, Angelfish, Guppies), as the G. ternetzi, a known "fin-nipper", will bite them to destruction, especially if its school is too small.

Aquarium Reproduction: Easy. Egg scatterers: the male furiously chases the female at dawn among fine-leaved plants (e.g. moss). They lay up to 1000 transparent eggs. Remove the parents immediately or they will devour the entire clutch in a few minutes.

Risks and Diseases: Armored fish against almost all pathologies if well managed. Sadly, this is the species used to create the monstrous "GloFish" (genetically modified for phosphorescence) or, worse, artificially injected with dyes, a cruel practice that lowers their defenses.