Rasbora Axelrodi Blue Axelrod Care Guide: Sumatran Blue
Tiny, electric blue, and almost impossible to photograph well — the blue axelrod is a 1.5 cm peat swamp specialist that turns dark tannin tanks into living constellations. Rasbora axelrodi, now correctly placed in genus Sundadanio as S. axelrodi but still widely traded under its old name, comes from Sumatran peat forest streams where water sits at pH 4-5 with conductivity barely measurable. Singapore keepers buying rasbora axelrodi from shop tanks at neutral pH frequently lose the entire shoal within a fortnight. This guide from Gensou Aquascaping at 5 Everton Park explains why and how to do it right.
Identification and Taxonomy
Sundadanio is a small genus of micro-rasboras separated from the main Rasbora line in 1999. Several species in the complex (S. axelrodi, S. atomus, S. echinus, S. gargula) are nearly identical and routinely mixed at export. The blue axelrod label usually refers to S. axelrodi proper, with bright blue iridescent flanks visible only against dark substrate and tannin-stained water.
Wild Habitat
Range covers eastern Sumatra and adjacent islands, with the type locality near Jambi. Habitat is shaded peat swamp forest stream margins, water pH 4.0-5.5, conductivity below 20 microsiemens, and 24-27°C. Substrate is decomposing leaf litter; visibility is often under 30 cm.
Tank Size and Aquascape
A shoal of 15-25 fish settles into 30-45 litres — these are tiny fish and need group strength rather than tank volume. Build around heavy leaf litter, fine dark sand, small driftwood pieces, and shade-tolerant plants. Floating frogbit dims the surface. Use ANS Catappa Leaves Small from the botanical range, layered three deep, and refreshed monthly.
Water Chemistry
Reverse osmosis remineralised lightly to GH 1-2 is mandatory. Acidify with peat extract and aged catappa tea to pH 4.5-5.5. KH must read zero. Singapore PUB tap is far too hard and alkaline. Temperature 24-26°C, with a small fan during peak Singapore heat to prevent thermal stress.
Filtration
Air-driven sponge on the lowest output. The QANVEE Bio Sponge Filter in the smallest size handles a Sundadanio tank. Heavy filtration creates current the fish struggle against, and at 1.5 cm body length they cannot tolerate even moderate flow.
Feeding
Tiny mouths require tiny food. Microworm, baby brine shrimp, crushed micro-pellet, vinegar eels and powdered fry food form the staple. The small fish food range includes some appropriate micro-pellets. Feed three or four small offerings daily — these fish have minimal reserves and starve quickly.
Group Behaviour
Sundadanio shoal loosely rather than tightly schooling. In groups of 10+ they spread across the tank, with males flashing blue iridescence in display chases. Below 10 fish they hide constantly and lose colour. Buy in larger groups than you think you need — losses during the first month are normal even with good husbandry.
Tank Mates
Best species-only. If combined, only the smallest, gentlest companions — Boraras brigittae, dwarf chocolate gouramis, or wild Parosphromenus — work. Anything larger than 3 cm or actively hunting will eat them.
Breeding
Egg-scatterers in fine moss or spawning mop. Adults eat eggs immediately, so harvest spawning material to a separate tank. Fry are minute and need infusoria for the first ten days. Breeding success in captivity is rare; most stock in trade remains wild caught.
Singapore Sourcing
Iwarna brings in Sundadanio shipments two or three times yearly at SGD 4-8 per fish. Buy 20+ at one go for shoaling success. Set up the system using a 30-45 cm cube from the aquarium tank range with tight glass lid, since these tiny fish jump through any gap.
Why Most Shop Stock Fails
Shops hold Sundadanio in neutral pH, hard water for sale convenience. Fish stressed in those conditions die within two weeks of purchase even when moved to perfect blackwater. Quarantine stock in soft, acidic water for two weeks before adding to the display tank, and accept some losses as the cost of working with a delicate wild import.
Related Reading
emilynakatani
Still Have Questions About Your Tank?
Drop by Gensou Aquascaping — most walk-in questions get answered in under 10 minutes by someone who has set up hundreds of tanks.
5 Everton Park #01-34B, Singapore 080005 · Open daily 11am – 8pm
