The Ruby Tetra is known only from the upper Rio Meta, a major tributary of the Rio Orinoco in Colombia. Few details are known of the natural habitat, but the favoured environments are thought to be sluggish or almost still, and crowded with dense vegetation and an abundance of leaf litter. The water is very soft and acidic, and stained a tea colour from the tannins in the decaying leaves and wood. The home aquarium should be mature, with a dark substrate and background and with driftwood and plenty of plant cover - both rooted and floating - in order for these peaceful fish to feel secure. Filtration should be efficient, but water movement gentle. Ruby Tetras are gregarious but not tightly schooling, and are best maintained in groups of at least 10, and more than this wherever possible. Male fish tend to hold small territories and may bicker a little on occasion, but providing there is a good network of hiding places/visual barriers for them to retreat into if necessary, no real harm should ensue. Tankmates, if desired, must also be small and peaceful. Good companions could include smaller species of Corydoras catfish, Otocinclus spp., dwarf cichlids, pencilfish, and other small blackwater tetras. If unfussy about creating an exact biotope, some of the smaller Rasbora and Boraras species from Asia would get along well with the tetras, as would Kuhli loaches (Pangio spp.). Acclimatisation should be carried out very carefully, and be sure to keep up with small regular water changes to keep nitrogenous wastes at a minimum, as these fish are very sensitive to deteriorating water conditions. In the wild, the Ruby Tetra has an all-over intense red colouration which diminishes somewhat in captivity - but the exact reason for this is unclear.