Goby fish - Stigmatogobius sadanundio

Scientific name: Stigmatogobius sadanundio

Common name: Goby fish

Family: Gobiidae

Usual size in fish tanks: 6 - 8 cm (2.36 - 3.15 inch)

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Recommended pH range: 7 - 8

Recommended water hardness: 8 - 18°N (142.86 - 321.43ppm)

0°C 32°F30°C 86°F

Recommended temperature range: 20 - 26 °C (68 - 78.8°F)

The way how these fish reproduce: Spawning

Where the species comes from: Southeast Asia

Temperament to its own species: peaceful

Temperament toward other fish species: peaceful

Usual place in the tank: Bottom levels

Overview

Stigmatogobius sadanundio, commonly called the Knight Goby or Goby Fish, is a small bottom-dwelling species native to South and Southeast Asia. It is best kept in lightly brackish conditions and is admired for its translucent body, dark markings, and peaceful yet predatory nature.

Care & Tank Setup

Tank size: A group of 4–6 specimens requires at least 75–100 l / 20–25 gal. Larger tanks allow more stable water conditions.
Water: pH 7.0–8.0, hardness 8–18 °dGH, temperature 20–26 °C (68–79 °F). They thrive in brackish water with SG 1.003–1.005, though short-term freshwater tolerance exists.
Aquascape: Provide fine substrate, smooth stones, caves, PVC tubes, and driftwood roots. Dim lighting and moderate flow help them feel secure.
Maintenance: Weekly partial water changes and careful monitoring of salinity keep them healthy.

Diet & Feeding

Knight Gobies are micro-predators. They prefer live or frozen foods but can adapt to high-quality prepared diets over time.

Staples: Frozen bloodworms, brine shrimp, mysis shrimp, and daphnia.
Supplements: Small pieces of shrimp or fish flesh, insect larvae.
Avoid: Tiny tankmates—they may be eaten. Pellets/flakes are often ignored unless pre-soaked and accepted gradually.

Behavior & Compatibility

Conspecifics: Peaceful in small groups if the tank has enough shelters. Males may spar but rarely cause harm.
Other fish: Suitable with brackish-tolerant mid-sized species (e.g., mollies, glassfish, larger rainbowfish). Avoid very small fish and delicate species.

Sexing

Males are usually more colorful with extended fins, while females display a paler, yellowish tone, especially when breeding.

Breeding

They are cave spawners. The female lays eggs on the roof of a cave, and the male typically guards them more intensively. Eggs hatch in 5–7 days, and fry can be raised on infusoria or rotifers, later on newly hatched brine shrimp.

Lifespan

With good care in stable, brackish conditions, the Knight Goby can live 4–6 years.

Origin

Native to India, Sri Lanka, Bangladesh, Myanmar, Singapore, and Indonesia, inhabiting estuaries, tidal rivers, and coastal streams where freshwater mixes with seawater.

Short description

A hardy but somewhat overlooked goby, Stigmatogobius sadanundio combines peaceful group dynamics with a predatory instinct. Best suited for a species tank or carefully chosen brackish community setups.