Neon Blue Rasbora Care Guide - Aquarium Setup, Diet & Breeding

The Neon Blue Rasbora is a minute, jewel-like schooling fish with a slender body and an electric blue stripe that catches the light as it moves. Its understated size makes the luminous colour seem especially striking, particularly against a dark background or subdued surroundings.

This species is an active but gentle shoaler. Groups spend much of their time weaving through plants and shaded areas, often displaying subtle interactions and flashes of colour as the males compete for attention. They are most confident and natural-looking when kept in a good-sized group.

Sundadanio axelrodi comes from forested blackwater environments where fallen leaves, roots and branches create a maze of cover. The water is typically very soft and acidic, with dissolved tannins giving it a tea-coloured appearance and reducing the amount of bright open water.

The species was formerly often sold under the name Axelrod's Rasbora and has also appeared in the aquarium trade as the Blue Axelrodi Rasbora. Its tiny adult size and peaceful nature make it a specialist favourite for carefully planned nano and biotope-style aquariums.

Neon Blue Rasboras are native to the island of Borneo in Southeast Asia, particularly the blackwater streams and peat-swamp habitats of Kalimantan, Indonesia. They are associated with slow-moving, tannin-stained waters beneath dense forest cover.

A group of Neon Blue Rasboras should have at least a 40-litre aquarium, with a footprint of around 45 by 30 cm or larger. Use a gentle filter current, dense fine-leaved planting, floating cover, driftwood and leaf litter to create shaded retreats, along with a dark sand or fine-gravel substrate. Soft, acidic, tannin-tinted water and subdued lighting suit their natural blackwater habitat, while a tightly covered aquarium helps prevent escapes.

Up to 2 cm (0.8 inches); females are usually slightly deeper-bodied and may be marginally larger than males.

Offer a varied diet of suitably tiny foods, including finely crushed quality flakes, nano granules, baby brine shrimp, daphnia, cyclops and other small frozen or live foods. Live and frozen foods help maintain condition and encourage natural colour and spawning behaviour, but every portion should be small enough for their minute mouths.

Neon Blue Rasboras are peaceful and best kept with similarly small, calm species such as celestial pearl danios, chilli rasboras, small pencilfish, pygmy Corydoras and peaceful freshwater shrimp. Avoid large, boisterous or predatory fish, including most larger barbs, gouramis and cichlids, as they may intimidate or consume these tiny rasboras. Their small fry and shrimplets are particularly vulnerable to predation.

Neon Blue Rasboras are egg-scattering fish that can breed in mature, soft, acidic water. Provide fine-leaved plants or spawning mops for the eggs, then remove the adults because they may eat them. The eggs usually hatch within a day or two, and the tiny fry initially need infusoria or another suitably fine first food before progressing to newly hatched brine shrimp.

Males are generally slimmer and show the strongest electric blue coloration, especially when displaying. Females tend to have a fuller abdomen and a less intense, often more greenish or subdued body colour, becoming noticeably rounder when carrying eggs.