South American Lungfish Care Guide - Habitat, Diet & Breeding

The South American Lungfish is a remarkable, eel-like freshwater fish with a long cylindrical body, small paired fins and a tapering tail. Its dark, mottled brown or olive colouring helps it blend into the leaf litter and muddy bottoms of its natural habitat. Unlike most aquarium fish, it can breathe atmospheric air using a highly developed lung-like organ.

Lepidosiren paradoxa is an ancient-looking species and one of the few living representatives of the lungfishes. It has a reduced skeleton, delicate thread-like fins and a flexible body suited to moving through dense vegetation and soft sediment. Its appearance has changed relatively little from that of its distant evolutionary relatives.

These lungfish inhabit quiet waters such as swamps, marshes, floodplain lagoons and sluggish tributaries. Many of these environments become extremely shallow or partly dry during seasonal droughts, and the species can survive difficult conditions by burrowing into the mud and relying on air breathing.

Despite their slow, seemingly placid movements, South American Lungfish are powerful predators. They use broad, crushing tooth plates to process hard-shelled prey and can become surprisingly bold and territorial as they mature. Their longevity and eventual size make them a specialist species rather than a conventional community aquarium fish.

South American Lungfish are native to slow-moving and seasonally flooded freshwater habitats across tropical South America, particularly the Amazon, Paraná and Paraguay river basins. Their range includes Brazil, Bolivia, Peru, Colombia, Venezuela, French Guiana and neighbouring regions.

A South American Lungfish needs an exceptionally large, secure aquarium or indoor pond of at least 3,000 litres for a full-grown specimen, with larger public-aquarium-scale housing preferable. The enclosure should provide a footprint of roughly 300 × 100 cm or greater, rather than relying on height alone, and must have a completely secure cover because this species is a powerful escape artist and needs access to atmospheric air. Use a deep layer of smooth, soft sand or fine mud-like substrate for natural burrowing behaviour, along with robust driftwood, smooth rocks and sturdy plants that cannot be easily uprooted. Leave generous open swimming space, provide strong biological filtration and avoid sharp decor.

Up to about 125 cm (49 in) in total length. Males and females are broadly similar in size, with no dependable sex-based difference in maximum length.

This carnivorous species naturally feeds on molluscs, crustaceans, aquatic insects, worms, small fish and other aquatic animals. In captivity, offer varied sinking carnivorous foods such as earthworms, prawns, mussels, crayfish pieces, quality predator pellets and appropriately sized whole foods. Avoid relying on fatty mammal or bird meat, and remove uneaten food promptly because large meals can create a substantial waste load.

South American Lungfish are best kept alone because they are large, predatory and capable of swallowing or seriously injuring tankmates. They may consume smaller fish, shrimp, snails, amphibians and other animals that fit into their mouth, while their strong jaws can damage slow-moving or delicate companions. If housed with other fish at all, tankmates must be similarly large, robust and peaceful, such as carefully selected large catfish or sturdy South American fish, with ample space and close monitoring. Even these combinations carry risk and are unsuitable for most aquariums.

Breeding South American Lungfish is extremely difficult in captivity and is rarely achieved in home aquariums. In nature, a bonded pair excavates a deep burrow in soft substrate during the rainy season, where the eggs are deposited. The male develops elongated, highly vascularised pelvic filaments that help oxygenate the nest, while the larvae initially possess external gills. Successful spawning requires a very large, mature setup with seasonal changes in water level and chemistry, plus suitable soft substrate for burrowing.

South American Lungfish are difficult to sex by appearance, and males and females are generally alike in body shape and colouring. During the breeding season, mature males develop elongated, richly vascularised filaments from the pelvic fins; females do not show this breeding-season structure.