Sundadanio axelrodi Green

The green form of Sundadanio axelrodi is collected from peat swamp streams in Sumatra, where it inhabits dark, tannin-stained, extremely soft and acidic water. It is distinguished from the blue Bornean form by its lime-green to yellow-green iridescence, though both forms display the same structural colour mechanism and similarly tiny adult size.

In the aquarium its care requirements are identical to the blue form: soft, acidic blackwater, very gentle filtration, dark substrate, and a group of at least fifteen individuals to display natural schooling behaviour confidently. The green iridescence is most vivid in natural or slightly warm-spectrum lighting against a black or dark brown substrate.

Both colour forms of Sundadanio axelrodi can be mixed in the same tank, creating a shimmering two-tone school of blue and green neon micro-fish. This combination in a well-aquascaped blackwater nano is among the most visually impressive displays possible in a small aquarium.

Water: Temperature 22–28°C, pH 4.0–6.5, GH below 6; peat-filtered or RO soft acidic water; Indian almond leaves or driftwood for tannins. Tank: Minimum 20 L nano; dark substrate; very gentle sponge filtration; no strong current. Feeding: Rotifers, micro-pellets, cyclops, and baby brine shrimp nauplii; only smallest food items appropriate for this micro fish. Breeding: Egg-scatterer; not reliably bred in captivity; pristine blackwater conditions are the most likely breeding trigger. Compatibility: Species tank ideal; can mix with blue form; avoid any fish larger than 3 cm that may outcompete or eat this species.