The Half-banded Spiny Eel is a great choice for those who keep a smaller aquarium!

The Half-banded Spiny Eel Macrognathus circumcinctus is one of the smaller spiny eels. Although not considered to be true eels, the body shapes of all members of the spiny eel family, Mastacembelidae, are definitely eel-like. It has a long pointy snout at the end of a elongated body.

If you’ve hesitated to purchase a spiny eel because of the size of your tank, this fish may be just what you are looking for. The maximum size for this handsome fish is just under 8 inches. Juveniles up to about 3 inches in length can be kept in about 10 gallons, but larger specimens will need a bigger area. Adults will need a tank that is 36 inches in length and about 35 gallons. Make sure you have a tight-fitting cover as these guys are escape artists.

This eel is one of the spiny eels occasionally referred and sometimes confused with the Tire Track EelMastacembelus favus and the Zig Zag EelMastacembelus armatus. Yet it has a uniquely different color pattern from the other Asian spiny eels. Rather than being a diamond or ‘zig zag’ type patterning, its markings are roughly vertical. This give is more of a banded appearance, and thus its common name. Other common names it is know by are Belted Spiny Eel and Large Spiny Eel. Large Spiny Eel is kind of a misnomer, as it is actually a very small eel!

Not only is the Half-banded Spiny Eel relatively small, it is also quite hardy once acclimated. You may not always see it though as it is nocturnal and sometimes will hide for long periods of time. Generally it’s a good community fish if kept with tank mates that are too big to fit in its mouth. Smaller fish, those under about 2 inches, may get snacked on.

Scientific Classification


Half-banded Spiny Eel – Quick Aquarium Care

Aquarist Experience Level:Intermediate
Aquarium Hardiness:Moderately Difficult
Minimum Tank Size:35 gal (132 L)
Size of fish – inches7.9 inches (19.99 cm)
Temperature:75.0 to 82.0° F (23.9 to 27.8&deg C)


Habitat: Distribution / Background

The Half-banded Spiny Eel Macrognathus circumcinctus (previously Mastacembelus circumcinctus) was described by Hora in 1924. They are found in Asia including Mekong and Chao Phraya basins, southeastern Thailand, Malay Peninsula, Sumatra, and Indonesia. This species is listed on the IUCN Red List as least concern (LC) because it is common throughout its range, and although harvested by fisheries and for the aquarium trade, there is no significant threats identified at present. Other common names they are known by are Belted Spiny Eel and Large Spiny Eel. They are also sometimes referred to as a Tire Track Eel or a Zig Zag Eel.

They inhabit the moving waters of rivers and streams with sandy to pebbly bottoms, normally with dense with vegetation. They also migrate during the dry season into canals, lakes and floodplain areas. They are nocturnal and will partially bury themselves in the substrate during the day, coming out at night to feed on invertebrates and small fish.

  • Scientific Name: Macrognathus circumcinctus
  • Social Grouping: Solitary
  • IUCN Red List: LC – Least Concern


The body of the Half-banded Spiny Eel is elongated with a pointed snout. Both the dorsal and anal fins are extended back to the caudal fin, which is very small. These fish will grow up to almost 8 inches (20 cm) and generally have a life span of 5 – 10 years, though they may live up to 15 years when given proper care.

The background coloration is a cream to light brown. Along the entire length of its body it is patterned with a series of irregular vertical dark markings. Its common name ‘half-banded’ is derived from the layout of its dark markings. On the upper two thirds of the body the markings are quite bold. Below that however, the markings become narrow extensions that reach either partially or entirely across the lower portion.

There is also a yellow form of M. circumcinctus. This variety has the black pigment either totally lacking or present only in small amounts.

  • Size of fish – inches: 7.9 inches (19.99 cm)
  • Lifespan: 15 years – These eels have a general lifespan of 5 – 10 years, though with good care may live up to 15 years.

Fish Keeping Difficulty

Eels are generally suggested for an aquarist with some experience rather than the beginner fish keeper. This eel can be a bit sensitive to change and usually takes awhile to get over its shyness. The first few weeks can be extremely difficult getting them to eat. These Eels are very shy when first introduced to a new environment and often die of starvation. It is best to feed these fish at night and make sure food makes it to the bottom.

They do require extremely pristine water. They have very small scales protecting their body so are prone to fungus and parasites and very sensitive to medications. These fish respond poorly to copper based medications, so these should be avoided. If cared for properly, these eels can live for a long time.

  • Aquarium Hardiness: Moderately Difficult – It is the initial few weekls that are difficult as they are nervous fish that take a while to be comfortable enough to eat.
  • Aquarist Experience Level: Intermediate

Foods and Feeding

The Half-banded Spiny Eels are carnivores. Like all spiny eels they prefer a diet of live and fresh frozen foods such as brine shrimp, black worms, earthworms or bloodworms. It might be trained to accept freeze dried alternatives although this is not always certain. They will also eat small fishes so make sure their tank mates are too large to be able to fit into their mouths.

This fish is nocturnal and likes to be fed after the lights are turned off for the night. Eels only need to be fed a couple of times a week and some may refuse food offered more than that, then often eating only once every two or three weeks. The middle and top inhabitants will often eat all the food before it sinks.

  • Diet Type: Carnivore –
  • Flake Food: No
  • Tablet / Pellet: Occasionally – Not all specimens will accept processed foods.
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Meaty Food: All of Diet
  • Feeding Frequency: Weekly – Eels only need to be fed a couple of times a week, and sometimes will eat even less.

Aquarium Care

The most important thing for these eels is that they always have clean and well-oxygenated water. Frequent water changes of about 30% a week are needed for this eel. With your weekly water change make sure to vacuum the gravel to remove all excess food and waster. but It’s best not to remove any bio film on rocks and decor. A magnet algae cleaner normally does a great job in keeping the viewing pane clear.

It is also helps to add efficient bottom cleaning tank mates to keep the bottom free from decaying foods in between cleanings. Be careful however, to add bottom cleaners after your eel is adjusted to its tank and is eating.

  • Water Changes: Weekly – Water changes of about 30% weekly.

Aquarium Setup

Half-banded Spiny Eels will spend most of their time on the bottom of the aquarium. Small specimens up to 3 inches can be kept in a tank that is about 20 inches long and about 10 gallons. Larger specimens will need a bigger area, tanks that are 36 inches in length and about 35 gallons will suit an adult.

They do best in a soft to medium-hard water with good movement that provides plenty of oxygenation. These fish require pristine water. The tank water should turnover at least 10-15 times per hour. An undergravel filter is a great choice for these fish as it creates high oxygen through out the tank as well as reducing the waste. A canister filter or powerheads and airstones can be introduced to achieve proper flow and oxygenation. Provide a tight fitting lid as spiny eels are escape artists.

They like a dimly lit aquarium or one with floating plants to help subdue the light. Provide a tank with a soft sand substrate as they will burrow into it especially if feeling threatened. Peat can also be used with the sand. Make sure they have plenty of hiding places among roots, rocks, or other decor so they will feel secure in their new home. Floating plant cover is great but plants buried in the substrate may get uprooted.

  • Minimum Tank Size: 35 gal (132 L)
  • Suitable for Nano Tank: No
  • Substrate Type: Sand – These eels have delicate skin so a soft and smooth substrate is needed.
  • Lighting Needs: Low – subdued lighting – In moderately lit tanks a lot of shaded hiding places are needed. Providing floating plants will also help subdue the light.
  • Temperature: 75.0 to 82.0° F (23.9 to 27.8&deg C)
  • Range ph: 7.0-7.5
  • Hardness Range: 5 – 15 dGH
  • Brackish: No
  • Water Movement: Moderate
  • Water Region: Bottom

Social Behaviors

They are a nocturnal species but are generally peaceful and shy. This fish is not very aggressive but due to their large size mouths, they may eat smaller tank mates. Fish under about 2 inches as small fish are part of their natural diet in the wild. They mostly ignore other tankmates, though some individuals will be markedly more belligerent.. Some species of spiny eels can get territorial and aggressive with their own kind so a general rule of thumb is to keep them singly unless you plan to breed.

These eels are very shy when first introduced to a new tank and are known to be too shy to eat at times. It is wise not to have tank mates like catfish or loaches, at least not until your spiny eel is settled in. These fish will simply take any food offered too quickly and the eel will not get comfortable enough to feed freely.

  • Venomous: No
  • Temperament: Semi-aggressive – Fish small enough to be eaten will be and Half-banded Spiny Eels or closely related species will rarely get along.
  • Compatible with:
    • Same species – conspecifics: Sometimes – Generally spiny eels should be kept singly unless the aquarist is hoping to breed them or has a large tank with enough room for each eel to have undisturbed territories. Then try to keep like sized fish together.
    • Peaceful fish (): Monitor – Fish small enough to be eaten will be, but fish over 2 inches are usually safe.
    • Semi-Aggressive (): Monitor
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Monitor
    • Large Aggressive, Predatory (): Threat
    • Monitor
    • Shrimps, Crabs, Snails: Threat – is aggressive
    • Plants: Monitor – Eels seem to enjoy digging and uprooting plants.

Sexual differences

Sexual differences are unknown and it is almost impossible to identify the sexes, though a mature female may be more full bodied.

Breeding / Reproduction

The Half-banded Spiny Eel has not been bred in captivity. Only a few spiny eels have been bred in the aquarium, possibly because they are generally kept singly rather than in a group where a male and female can find each other. Though it is not documented what makes them spawn, trying to emulate the bounty of the flood season can help stimulate breeding behavior. Feed more and higher quality food than you normally would and providing an influx of clean water. Their courtship lasts for several hours, where they chase each other and swim in circles.

The eggs are deposited among floating plants. They are sticky so will adhere to the plants and then hatch in 3 to 4 days. The fry becoming free swimming a few more days after that and should be fed nauplii. The fry are something of a challenge to raise as they are susceptible to fungal infections. Regular water changes and the use of an antifungal water treatment can help.

  • Ease of Breeding: Unknown

Fish Diseases

Eels are prone to diseases caused by parasites and fungus, so take caution when introducing these fish to an established tank. Eels are also very sensitive to medications used to treat many diseases; a separate hospital tank is needed. Very low water temperatures and condition changes can also cause stress to this fish which makes them even more prone to disease. Take great care when netting eels as they have very delicate and scraps can make them even more prone to disease.

The most common disease that an eel is susceptible to is Ich. Ich is short for Ichthyophthirius, also known as “white spot disease”. It is a parasite that can attack nearly all aquarium fishes, but you’ll find that Eels are often the first to be attacked. Take great care in treating ick as eels are very sensitive to the medications used to treat it. Often the dose is half of what is normally used. If nervous or unsure about medications, use Reef safe medications.

An outbreak of disease can often be limited to just one or a few fishes if you deal with it at an early stage. When keeping these sensitive types of fish, it is common to catch deteriorating water conditions and disease before other fish are affected. The best way to proactively prevent disease is to give your Half-banded Spiny Eel the proper environment and give them a well balanced diet. The closer to their natural habitat the less stress the fish will have, making them healthier and happy. A stressed fish will is more likely to acquire disease.

Anything you add to your tank can bring disease to your tank. Not only other fish but plants, substrate, and decorations can harbor bacteria. Take great care and make sure to properly clean or quarantine anything that you add to an established tank so not to upset the balance. It is recommended to read up on the common tank diseases. Knowing the signs and catching and treating them early makes a huge difference. For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.


The Half-banded Spiny Eel is commonly available and reasonably priced.



Featured Image Credit: Arunee Rodloy, Shutterstock