Ruby tetra

Geographic Origin and Biotope: Native to the Meta River basin in Colombia. It is a typical inhabitant of very slow forest streams, rich in humic acids (light "Blackwater") and completely shaded by riparian vegetation.

Taxonomy and Morphology: Ruby Tetra (Axelrodia riesei). An exceptional dwarf characin. The body is microscopic and slightly compressed, characterized by a huge eye compared to the proportions of the head and by the absence of an adipose fin.

Social Behavior: Extremely shy and gregarious. Forms cohesive schools of dozens of individuals that move in unison in the lower third of the tank. If isolated (less than 10 specimens) it rapidly wastes away due to acute stress.

Coloration and Sexual Dimorphism: Spectacular intense and translucent ruby red, with a peculiar dark spot at the base of the tail surmounted by a luminescent dot. Males are redder and more slender; females, although colored, are noticeably more swollen in the abdomen.

Aquarium Setup: Very mature nano-aquarium (min. 45 cm / 18 inches). Very slow filtration is indispensable (they do not like current) and a thick forest of plants (Mosses, Microsorum). Intense light will make them discolor and hide: use wood and leaves to amber the water.

Diet and Feeding: Micro-predator. Due to its tiny mouth, it struggles to eat classic commercial flakes. The ideal diet consists of live brine shrimp nauplii, microworms, rotifers and floating protein powders rubbed between the fingers.

Water Quality: Very delicate. Demands very soft (KH close to zero) and acidic (pH 5.0-6.5) waters. The presence of nitrates or sudden thermal shocks cause sudden die-offs of the school.

Compatibility and Tankmates: Can only cohabit in "Peaceful Nano-setups". Excellent with Corydoras pygmaeus, Otocinclus and Caridina shrimp (whose zoeae are safe thanks to the tiny size of the fish). A single Dwarf Cichlid (even a placid one) will terrify them to death.

Aquarium Reproduction: Rare. They lay very small eggs among the mosses at very low pH (under 5.5). The parents offer no care, but in very thick tanks some microscopic fry can survive feeding on natural infusoria.

Risks and Diseases: Acclimation shock: they are famous for dying en masse during transfers or fast introductions into the tank. Prolonged drip acclimation (over 2 hours) is the only safe method.