Because they are able to cling to various surfaces in fast moving waters, the Mongoose Loach is sometimes called a Lizard Loach!

The Mongoose Loach Nemacheilus rueppelli is especially designed to cope with living in fast waters. LIke a lizard, especially a gecko, it is able to cling to various surfaces and hence is also known by the more generalized common name Lizard Loach.

It has occasionally been referred to at the Long Shounted Loach as well. Its easy to understand “long” and “loach” as they are quite descriptive of this fish, but what the term “shounted” means is unknown.

This lizard loach has an attractive pattern over a silver to light golden background. The patterning of the Mongoose Loach consists of dark spots on the the head back to about the pectoral fins. It then becomes dark bands along the rest of the body, through the tail, and on the dorsal fin. The bands between the pectoral and dorsal fin and the bands before the tail are interspersed with short vertical stripes.The fins are translucent.

These are Hillstream Loaches, meaning they come from cool fast-moving streams. The Mongoose Loach will do best in a cooler “river” type aquarium kept with good water movement and subdued lighting. Provide a large grain sand or small gravel substrate. Be sure to provide plenty of hiding and resting places created with round river type rocks and driftwood. A moderate amount of plants can be a nice addition but leave a large open area for swimming.

The Mongoose Loach is a peaceful community fish and enjoys the company of other non-aggressive tank mates. They also enjoy the company of their own species and are best kept in a group of five to seven, with the suggested minimum being three.

For Information on keeping freshwater fish, see:
Freshwater Aquarium Guide: Aquarium Setup and Care

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Cypriniformes
  • Family: Balitoridae
  • Genus: Nemacheilus
  • Species: rueppelli
Mongoose Loach – Quick Aquarium Care
  • Aquarist Experience Level: Intermediate
  • Size of fish – inches: 4.9 inches (12.50 cm)
  • Minimum Tank Size: 30 gal (114 L)
  • Temperament: Peaceful
  • Aquarium Hardiness: Moderately Difficult
  • Temperature: 65.0 to 75.0° F (18.3 to 23.9&deg C)
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Habitat: Distribution / Background

The Mongoose Loach Nemacheilus rueppelli was described by Sykes in 1839. They are found in Asia, in tributaries of the Krishna River in northern Western Ghats of Maharashtra and Karnataka, India. Other common names it is called include Long Shounted Loach and Lizard Loach.

This loach is listed on the IUCN Red List. Nemacheilus rueppelli is a widely distributed species and in some areas the species has faced drastic declines due to increasing urbanization and pollution of these rivers. But because there are a number of locations where it is found that indicate no wide spread threats, it currently is listed as Least Concern (LC).

This Long Shounted Loach is found in main river channels and tributaries. They tend to stay in swift flowing clear stretches of rocky substrate. Their habitat is normal absent of aquatic plants. In nature this loach feeds on crustaceans, insects, larvae, and plant matter.

  • Scientific Name: Nemacheilus rueppelli
  • Social Grouping: Groups
  • IUCN Red List: LC – Least Concern


The Mongoose Loach will get up to 5 inches (12.5 cm) in the wild, though in the aquarium it is usually smaller and has a life span of up to 10 years. This loach has a long slender snout and long body. The body is a silver to light golden background. The patterning consists of dark spots on the the head back to about the pectoral fins. It then becomes dark bands along the rest of the body, through the tail, and on the dorsal fin. The bands between the pectoral and dorsal fin and the bands before the tail are interspersed with short vertical stripes.The fins are translucent.

  • Size of fish – inches: 4.9 inches (12.50 cm) – Will normally be smaller in captivity.
  • Lifespan: 10 years

Fish Keeping Difficulty

This loach can be hardy under the right conditions. They are not recommended for beginners because of their need for pristine water and they do not have scales. Not having scales make them more prone to disease and very sensitive to medications used to treat disease. Experience in treating scaleless fish is very important to be able to give your loach a healthy and long life.

  • Aquarium Hardiness: Moderately Difficult
  • Aquarist Experience Level: Intermediate

Foods and Feeding

The Mongoose Loach is an omnivore and feeds on crustaceans, insects, larvae, and plant matter in the wild. In the aquarium this loach will generally eat all kinds of live foods, sinking pelleted and tablet foods, flakes, and algae. They like frozen foods as well. To keep a good balance give them a high quality flake or tablet food everyday. Feed mosquito larvae, brine shrimp (either live or frozen), tubifex, daphnia, and some vegetable foods such as algae wafers. As this fish spends its time on the bottom of the aquarium, make sure the food reaches the bottom.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Some of Diet
  • Feeding Frequency: Several feedings per day – Make sure the food reaches the bottom.

Aquarium Care

For this loach to thrive, it is most important that the water be clean and well-oxygenated. The use of an over-sized filter is a minimum requirement. Weekly water changes of at least 30% are also needed to keep the loach healthy.

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

Aquarium Setup

The Mongoose Loach will swim in the bottom of the aquarium. Because this loach does best in groups, a larger tank (ideally 30 gallons or so) will work best. The tank needs to have ample hiding places for this shy fish to retreat such as rocks, caves, and roots. They do best in soft, slightly acidic water.

The tank setup for the Lizard Loach should resemble its natural habitat, slow moving rivers. The substrate can to be a fine or medium gravel. Larger smooth rocks, driftwood and branches should be added to provide shade and places for quick retreat. Java Ferns can be introduced and will attach to the decor. Powerheads or a rivertank manifold can be added to provide a unidirectional flow to simulate its natural habitat.

Most importantly the water must be clean and well-oxygenated so we suggest the use of an over-sized filter as a minimum requirement. A high quality canister filter is best and will clean as well as help create water movement. Installation of a rivertank manifold is recommended, though not essential, as it would not only provide an excellent alternative/additional form of filtration but bring with it the benefit of unidirectional water movement and more closely simulate what the fish experience in nature. Water turnover should ideally be in excess of 20 times per hour so additional powerheads/airstones can be used to achieve the desired flow and oxygenation in the absence of such a device.

  • Minimum Tank Size: 30 gal (114 L)
  • Suitable for Nano Tank: Sometimes
  • Substrate Type: Sand/Gravel Mix – Must be smooth.
  • Lighting Needs: Low – subdued lighting
  • Temperature: 65.0 to 75.0° F (18.3 to 23.9&deg C)
  • Range ph: 6.5-7.0
  • Hardness Range: 2 – 12 dGH
  • Brackish: No
  • Water Movement: Strong
  • Water Region: Bottom – These fish are mostly bottom dwellers.

Social Behaviors

A good community fish, they are peaceful and will do well with non-aggressive tank mates as well as enjoy other members of their own species. It is recommended that they be kept in groups of at least 3, with larger groups of five to seven being recommended.

  • Venomous: No
  • Temperament: Peaceful
  • Compatible with:
    • Same species – conspecifics: Yes – This fish likes to be housed with its own kind, ideally in group of three to seven.
    • Peaceful fish (): Safe
    • Semi-Aggressive (): Monitor
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Threat
    • Monitor
    • Shrimps, Crabs, Snails: Safe – not aggressive
    • Plants: Safe

Sex: Sexual differences


Breeding / Reproduction

They are not yet bred commercially. There have been reports that some species of Hillstream Loach will breed in pits dug under rocks in a ‘river’ type environment, but there are no reported aquarium spawnings.

  • Ease of Breeding: Unknown

Fish Diseases

The Mongoose Loaches are scaleless and prone to disease, so take caution when introducing these fish to an established tank. This loach is also very sensitive to medication to treat many diseases, a separate hospital tank is needed. Cold water and condition changes can also cause stress to this fish which makes them even more prone to disease.

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 Lizard Loach 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 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 Mongoose Loach is occasionally available.