Very often, fishkeepers have a desire to have some unusual fish in their aquarium. Often the choice is limited to representatives of the genus Macrognatus. These fish are similar to eels, have a long ribbon-like body and a pointed Mastacembelidae mouth. And their feature burying themselves in the ground, leaving only the head on the surface, can surprise any aquarist.

Scientific nameMacrognathus
Common namesMacrognathus, Lesser spiny eel, Peacock eel, eels, loaches, catfish
Southeast Asia and India
Size15 cm or 6 inch in aquarium
Tank size50 L ( 13 gallons ) for small fish / 120 L (31 gallon ) for adults
Life span5 - 10 years
23-26 C. or 73-79°F
pH 6.0 – 8.0
GH 6-35
Colorgray, dark brown, or beige, yellow with different spots colors
Foodsmall invertebrates, insect larvae, and worms, frozen food
Breedingvery hard / used with hormonal injections / different aquarium
Temperamentvery timid especially when young
at age of 1 to 2 years
Eggsup to 1000 eggs with size of 1.25 mm / 3-4 days incubation

General information

Macrognatus belong to the family of Mastacembelidae. They got this name for the unusual shape of the mouth: the upper jaw is elongated and pointed, forming a kind of proboscis. The name of the genus comes from the Greek words “macros” (large) and “gnathos” (jaw) and indicates their unusual mouth, which can be stretched to swallow large food. In the sale of macrognatuses, they are often called eels, loaches, catfish, but this is a completely separate genus of fish.

They are mostly nocturnal. While waiting for prey or resting during the day, they prefer to dig into the ground with their whole bodies, while their heads are left for observation. Regular digging also removes excess mucus, which is constantly released on the skin of the fish. Powerful mucus also helps in the event of an accidental hit on land, where the fish can exist for about an hour.

Macrognatus growing in nature up to 40 cm, in some Asian countries are a commercial species, their meat is considered a delicacy. Since species of the genus are sometimes very similar in appearance to one another, their identification is difficult and confusion often arises in the definition.

Watch this video of macrognatus roaming in an aquarium:

Macrognathus pancalus


The body is elongated, acne-shaped, the front part is pointed, and forms the proboscis. The tail is medium-sized rounded. The dorsal and anal fins are long, they are placed in the lateral place of the body, the pectorals are transparent, and the abdominal are poorly developed.

Fish can be painted in gray, dark brown, or beige. Black rounded spots with a border of white or yellowish color are sometimes located near the tail. Similar spots are found on the dorsal fin, their number varies and can range from 3 to 7.

The whole body is covered with a pattern of shiny transverse dots and stripes. On the side of the body, there is a barely noticeable longitudinal strip from head to tail.

Sexual dimorphism is not expressed. Females have a larger size and a large rounded abdomen.


The natural habitat of macrognathus includes Southeast Asia and India. Most often, fish are found in the river basins of the Mekong and Chao Phraya River, as well as on the islands of Borneo and Sumatra. They prefer to stay on sandbanks of slow-flowing water bodies. Here they burrow into the sand and wait for prey.

Types of macrognathus

Lesser spiny eel ( Macrognathus aculeatus )

This fish can also be found under the name “prickly eel” because of the sharp spikes of thorns located on the dorsal fin. In nature, aculeatus macrognaths can grow up to 40 cm, but in aquariums usually no more than 20 cm. Anal and dorsal fins are well developed, stretching to a small tail. The body color varies from yellow to light brown, transverse dark stripes can be detected. A thin light stripe stretches from head to tail. On the back of the body, there are large black spots with a light border.

They have a twilight lifestyle. For maintenance, you need an aquarium with a volume of 80 liters. Reproduction is possible only with the use of hormonal drugs.

The Half-banded eellllllll ( Spiny Eel Macrognathus circumcinctus )

One of the smallest representatives of a kind. The maximum size of circumcinctus macrognathus in the aquarium reaches 15 cm. Very hardy appearance. Leads a secretive lifestyle, comes up for food after turning off the lights in the aquarium. Like other representatives of the genus, it is an ambush predator. It is not recommended to plant fish with a size of less than 5 cm – they can easily become a victim of an adult macrognathus.

The main body color is light brown or coffee with cream spots. On the sides are transverse stripes.

It can be contained in groups. For young individuals, an aquarium of 50 liters is suitable, for adults it is better to allocate a capacity of at least 120 liters. The optimal soil is sandy; it is easiest for fish to dig into it. The aquarium needs good filtration and aeration. Spawning is stimulated by gonadotropic drugs.

Peacock eel ( Macrognathus siamensis )

Large macrognatus, under suitable conditions, can grow up to 25-30 cm. The body is light brown in color with several pale yellow stripes along the lateral line. On the dorsal fin, from 3 to 6 large roundish spots are located, for which the fish is often called “peacock eel.”


To maintain the siamensis macrognathus, you need an aquarium of at least 100 liters with sandy soil and a large number of shelters (snags, stones) is required. Living plants are necessary, but there must always be free areas for swimming. Reproduction in the aquarium is difficult.

Care and maintenance

The vast majority of macrognathus are very large fish and like to swim. Therefore, it is necessary to choose an aquarium of at least 80 liters, and if you plan to contain several individuals, then at least 130 liters. The aquarium must be equipped with a lid: a unique feature of macrognathus is the ability to find even the smallest gaps and crawl out of the tank. This happens especially often in aquariums equipped with an external filter – the macrognathus can escape through the hose holes.

It is important to ensure high-quality filtration and aeration in the aquarium because macrognathus are very fond of clean water. The current should be moderate and the lighting not very bright. Intense lighting is an additional stress for fish, as these species are twilight, and the peak of their activity occurs in the evening after turning off the lights. It is very convenient to watch the life of fish in aquariums equipped with special night (blue) lighting, for example, Tetra AquaArt LED.

Particular attention must be paid to the selection of soil. The physiological feature of macrognathus is the release of a large amount of mucus on the integument. Excesses of this mucus must be regularly removed, otherwise, they can lead to skin diseases. To remove mucus, fish are regularly buried in the ground. Stony soils with sharp edges are not suitable for the maintenance of macrognathus, it will be difficult to dig into it, and fish can easily damage their delicate skin. The best choice will be large washed sand or small rounded pebbles.

As for decorations, you can use natural driftwood, rounded stones, and artificial decorations without sharp edges.

Weekly water changes up to 30% of the volume of the aquarium are required.

The optimal water parameters for the content of macrognatuses: T = 23-26 ° C, pH = 6.0-8.0, GH = 6-35.

Macrognatus calmly refer to living plants in the aquarium, but it is worth considering that they are able to dig up the roots of some species. When planting plants, it is necessary to leave free “clearings” on which the fish will dig into the sand. With the exception of ground cover, any plant species can be planted in aquariums with macrognathus, but it is better to prefer species with a large root system, such as echinodorus and cryptocoryns.


Despite the predatory way of life in nature, in aquariums, macrognathus (especially young ones) are rather timid fish that are quite calm about their neighbors in the aquarium. The only exceptions are individuals that can fit in the mouth – they will hunt for such macrognathus at night. Young macrognathus feel great in flocks, adults become territorial, so it is better to keep them alone.

Suitable roommates will be gourami, Rainbowfish, large Xiphophorus, calm cichlids, Ancistrus, Cory catfish. It is not recommended to keep macrognathus and active bottom fish in the same aquarium – Botia, thoracata, between them there will be a struggle for a territory from which macrognathus are unlikely to emerge victorious.

Macrognathus feeding

In nature, macrognathus feed on small invertebrates, insect larvae, and worms. Often they hunt from ambush for small fish.

When kept in aquariums, they usually use natural frozen food (bloodworms, Sludge worm, artemia). Some are able to take finely chopped slices of shrimp, squid, and cod. Unfortunately, feeding complete dry feed is not always possible. But some individuals are accustomed to eating large flakes, granules or chips, for example, TetraMin or TetraPro Energy. There is also a safe alternative to live food – the Tetra FreshDelica series. These are popular food organisms (bloodworms, artemia, daphnia, and kriel) in very tasty and nutritious jelly.

When feeding, one should take into account the nocturnal lifestyle of macrognathus. It is best to give food after turning off the light so that other fish can not eat it first. It is necessary to strictly monitor that each macrognathus gets a portion of food, otherwise, this can lead to the depletion of the most timid individuals. Fish prefer to eat in the lower layers of the aquarium, but if necessary they swim for food to the surface. Individual individuals eat food from their hands, swimming to the owner.

Breeding and breeding

Breeding macrognathus in an aquarium is difficult. This is due to the natural features of spawning: it occurs during the rainy season, when the water parameters in the rivers change greatly.

For artificial breeding, hormonal injections are used. First, parents are selected, which are planted in a separate container and actively fed with high-protein feed. A spawning aquarium is being prepared at this time. Aquarium of 200 liters and a length of at least one meter is recommended. A mesh is laid at the bottom, bushes of small-leaved plants are planted on top – Java moss, Bolbitis heudelotii or Microsorium pteropus, it will also be useful to place several shelters in the spawning grounds.

In a spawning aquarium, it is necessary to organize good filtration and aeration. The course should be moderate or strong. Water hardness is set less than in the main aquarium – this will serve as an additional incentive to spawn, simulating the onset of the rainy season.

After the female’s abdomen begins to swell, it and one or two males must be put into a spawning ground, after having previously injected a gonadotropin into the spinal muscle. Then the aquarium is shaded and the fish are left alone.

Spawning itself can last several hours. Males actively chase the female around the aquarium, forcing them to throw eggs, which are then fertilized. One female is able to lay up to 1000 eggs with an average size of 1.25 mm. After spawning, producers need to be jailed.

The incubation of eggs lasts 3-4 days. The yolk sac larvae feed for the same amount of time, after which they go on to self-feed. At this time, the greatest danger for young macrognathus is fungal infections, therefore, regular water changes and the addition of antifungal drugs are necessary.

As the juveniles grow, they must be sorted by size and planted. Puberty in fish occurs at the age of 1-2 years.