Ruby Tetra

Axelrodia reisei is a jewel-like micro-tetra from the blackwater streams of the upper Orinoco and Rio Negro watersheds in Venezuela and Brazil. The entire body glows with an intense ruby-red translucence that is among the most vivid of any small tetra, matched in intensity only by the Ember Tetra but surpassing it in pure saturation under appropriate lighting.

Successful keeping requires a dedicated blackwater setup: very soft, highly acidic water (pH 4.5–6.0), warm temperatures, dark substrate, heavy tannins, and minimal flow. This is unambiguously an advanced species for the experienced aquarist comfortable maintaining extreme soft-water conditions. In such an environment, large groups of twenty or more create a breathtaking ruby cloud effect.

Feeding must be tailored to the fish's tiny mouth: commercial micro-pellets, infusoria, Cyclops nauplii, and smallest baby brine shrimp are required. Standard flake is too large and should not be offered.

Water: 25–28°C, pH 4.5–6.0, extremely soft (GH 0–4, KH 0–2); heavy tannins mandatory. Tank: 40 L minimum; species or near-species tank; blackwater with botanicals, dim lighting, zero flow. Feeding: Micro-pellets, infusoria, Cyclops nauplii, baby brine shrimp nauplii only — tiny mouth. Breeding: Rarely achieved; requires pristine ultra-soft acidic conditions and very small live foods. Compatibility: Only with similarly tiny, peaceful blackwater species; avoid anything larger.