Sleepy Trout, Australian Gu (Mogurnda mogurnda) — 4,5-5cm

Overview

The Mogurnda mogurnda, commonly known as the Sleepy Trout, Northern Trout Gudgeon, or Australian Purple-Spotted Gudgeon, is a hardy, colorful freshwater fish UK specialist species native to northern Australia and New Guinea. Growing to around 8 cm in captivity, this bold semi-aggressive gudgeon displays fascinating bottom-dwelling behavior and stunning coloration. At Tropical Fish Co, we supply healthy juveniles that adapt well to aquarium life and reward attentive care with years of engaging, active behavior.

Appearance and Coloration

Mogurnda mogurnda displays a robust, slightly compressed body with a base color ranging from olive-brown to golden-yellow. The most distinctive feature is the series of purple or violet spots scattered across the flanks and fins, creating a shimmering effect under subdued lighting. The dorsal and caudal fins are large and ornate, with dark banding and iridescent highlights. The head is broad with large eyes and a wide mouth. Males are more colorful than females, with more intense spotting and larger fins. Juveniles at 4.5–5 cm show similar but less intense coloration, which develops fully as they mature.

Natural Habitat and Distribution

This species inhabits slow-moving rivers, streams, billabongs, and wetlands in northern Australia and New Guinea. Water conditions are typically warm (22–28 °C), neutral to slightly alkaline, and well-oxygenated. The substrate is sand or mud, and the environment features submerged logs, rocks, and dense aquatic vegetation. Mogurnda mogurnda is primarily bottom-dwelling, hiding among rocks and logs during the day and emerging at dusk to hunt for small fish, invertebrates, and crustaceans. The natural environment is dimly lit with slow to moderate current and abundant hiding places.

Aquarium Setup and Décor

A 100-litre aquarium is suitable for a pair or small group of Mogurnda mogurnda. Provide plenty of caves, driftwood, and shaded hiding spots, as this species can be territorial and may prey on very small tankmates. Use sand or smooth gravel substrate, and include live or artificial plants such as Java fern, Anubias, and Vallisneria. Subdued lighting is preferred. A secure lid is recommended, as gudgeons are strong swimmers and may jump. Keep water clean and well-oxygenated with regular water changes. Provide multiple hiding spots to reduce territorial aggression, especially if keeping more than one male.

Feeding and Nutrition

Mogurnda mogurnda is carnivorous. Offer a varied meaty diet including quality sinking carnivore pellets, frozen or live bloodworms, mysis, brine shrimp, daphnia, and chopped earthworms or insect larvae. Occasional small crustaceans or chopped fish can be offered. Feed once or twice daily in small portions, ensuring food reaches the substrate. This species is a predatory feeder and will consume any tankmate small enough to fit in its mouth. Avoid overfeeding, as uneaten food can degrade water quality. Once acclimated, most individuals will accept high-quality sinking pellets.

Behaviour and Social Structure

The Northern Trout Gudgeon is semi-aggressive and territorial, especially toward conspecifics or other bottom-dwellers. Males are particularly territorial and will establish and defend territories against rivals. This species is primarily bottom-dwelling, hiding among rocks and logs during the day and emerging at dusk to hunt. It may prey on very small tankmates and can be assertive at feeding time. Despite its territorial nature, it is not overly aggressive toward tankmates of similar size that occupy different tank zones. Pairs may form and spawn in caves or sheltered sites; males typically guard eggs and fry.

Compatible Tank Mates

Ideal companions include robust, similarly sized peaceful fish such as large peaceful rainbowfish (Boesemani, turquoise), hardy barbs of similar size (tinfoil, rosy), and non-aggressive bottom-dwellers too large to be eaten. Avoid housing with small fish, shrimp and other small invertebrates, slow-moving or long-finned fish, very aggressive cichlids, or tiny fry or nano species. Fast-moving, mid-water species that will not be harassed are best.

Breeding in the Aquarium

Pairs may spawn in caves or sheltered sites; males typically guard eggs and fry. Provide clean water, hiding places, and a protein-rich diet to encourage breeding. Males are more colorful and larger-finned than females. Spawning occurs on cave ceilings or inside narrow crevices, and the male fans and guards the eggs until hatching. Remove the female after spawning to prevent aggression from the guarding male. Fry require specialized care and high-protein micro-foods such as infusoria or liquid fry food initially, graduating to micro-worms and baby brine shrimp.

Why Buy from Tropical Fish Co

At Tropical Fish Co, every Sleepy Trout is quarantined, health-checked, and acclimated to UK water conditions before dispatch. We source our fish from reputable suppliers who prioritize ethical collection and sustainable practices. Our livestock arrives in insulated packaging with heat packs during colder months, ensuring safe transit. With decades of combined fishkeeping experience, our team is available to answer questions about care, compatibility, and tank setup. Whether you're building an Australian biotope or expanding an established collection, we're here to support your success. Order with confidence and enjoy premium freshwater fish delivered to your door.