Axelrod's Blue Rasbora (Sundadanio axelrodi) Breeding Guide

Sundadanio axelrodi is a tiny egg-scatterer from Borneo peat swamps, rarely bred and demanding stable, very soft, acidic blackwater in heavily planted mature tanks.

Overview

Sundadanio axelrodi, Axelrod's blue rasbora, is a tiny iridescent cyprinid from peat swamp forests of Borneo. According to Seriously Fish it is an egg-scatterer that has not been bred often in the hobby, with success requiring conditions maintained in heavily planted, mature aquaria.

Sexing

Seriously Fish reports that males are more colourful and noticeably slimmer than females, showing dark or red colour in the anterior anal fin depending on colour form, and can produce audible croaking sounds when stressed. Females are less colourful with a deeper body and a colourless anal fin.

Conditioning

Because the species does not tolerate fluctuating conditions, conditioning is best done within the stable mature tank rather than moving fish to a separate spawning aquarium. Stable parameters are emphasised as critical throughout.

Breeding Setup

Seriously Fish recommends a heavily planted, mature aquarium with blackwater simulated using leaves and real peat fibre, which it describes as highly beneficial. Bright lighting is best avoided. Suggested values are temperature 23-26 C, pH ideally below 6.0 (general range 4.0-6.5) and hardness 0-5 dH.

Spawning Behavior & Trigger

Rather than a discrete trigger, Seriously Fish indicates that fry should start to appear without further intervention provided the tank offers adequate cover and microfauna, in line with the species' egg-scattering reproduction.

Egg & Fry Care

Microorganisms within the blackwater environment provide a valuable secondary food source for the fry, supporting their early development within the mature planted tank.

Common Challenges

The principal challenge is the species' intolerance of fluctuating water conditions, which makes a separate spawning tank difficult to arrange; very soft, acidic, stable blackwater in a mature planted aquarium is required for any success.