The Ruby Tetra is among the most brilliantly colored of all nano tetras, and among the most demanding in terms of water chemistry. At a maximum of 2 cm, it is one of the smallest tetras commonly available in the hobby, but what it lacks in size it more than compensates for in visual impact: the entire body suffuses with an intense ruby-red to rose-pink coloration that appears almost to glow from within, particularly when the fish is in good health and kept in appropriately tinted blackwater conditions. Native to the meta and Orinoco river drainages in Colombia, this species inhabits slow, shaded blackwater streams with extremely low mineral content. It absolutely requires soft, acidic water — ideally pH 4.5–6.0 with near-zero hardness — and will fade rapidly, become prone to disease, and decline in hard, alkaline conditions. For hobbyists able to provide the correct water chemistry, however, the Ruby Tetra is a spectacular and rewarding species. It should be kept in large schools of eight or more in a dedicated nano or blackwater biotope aquarium, away from larger fish that would easily consume it. Micro-foods are essential as its tiny mouth cannot accept standard flake.
