Pearl sundadanio

Sundadanio margarition

Also known as Little pearl sundadanio

FreshwaterFish

Pearl sundadanio (Sundadanio margarition) — The Wet Spot Tropical Fish · Used with permission

Care at a glance

Temperature: 73–81°F (23–27°C)
pH: 4.5–6.5
Adult size: 0.9 in (2.4 cm)
Minimum tank: 11 gal (40 L)
Temperament: Peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Difficult
Breeding: Hard
Rarity: Rare
Origin: Rajang and Sarawak basins, Malaysian Borneo
Family: Danionidae

Overview

This is a tiny, delicate blackwater fish that only looks its best in a group, so keep at least ten together in a quiet, mature tank. It shoals in the middle water and is entirely peaceful, but it is too small and particular to mix with anything boisterous; the safest companions are other micro species that share its soft, acidic water, or no tankmates at all. Feed very small foods several times over, such as microworm, baby brine shrimp, cyclops, and finely crushed flake. A planted, shaded tank of around 40 liters is enough for a shoal, provided water quality stays high.

In the wild

The pearl sundadanio lives in blackwater peat-swamp streams of the Rajang and Sarawak drainages in Malaysian Borneo, water stained dark by tannins, very soft and acidic, moving slowly under shade. Match that with a dim, gently filtered tank over dark substrate, with leaf litter, botanicals, or peat to lower and hold the pH. Keep the temperature between 23 and 27 C and the pH from 4.5 to 6.5.

Good to know

Sundadanio margarition belongs to the family Danionidae and matures under 2.5 centimeters, among the smallest fish in the trade. Its name means little pearl, for the nacreous sheen along its flanks. It was one of several species split from the old catch-all Sundadanio axelrodi in a 2011 revision of the genus. Breeding is difficult: it is an egg-scatterer that needs stable, very soft, acidic water, and tiny live foods to raise the fry.

Did you know

The name margarition is Greek for a little pearl, and a shoal of them drifting over dark peat really does look like a string of small pearls come loose in the water.