Obtain a colorful Rainbow Loach, and you will have a truly spectacular eye catcher!

The Rainbow Loach Micronemacheilus pulcher (previously Traccatichthys pulcher, Nemacheilus pulcher) is a fairly large river loach. It is a slender, elongated fish that can reach between 4 – 4 3/4 inches (10 – 12 cm) in length. Generally though it will be on the smaller size in the aquarium.

This is a loach with a lot of color potential. It is also known as the Beautiful Hillstream Loach and the Mountain Loach and depending on the specimen you have, it can range in brilliance from rather plain looking to very colorful. The common names quickly depict the beauty this fish is capable of with a good colored specimen.

Overall this loach has a greenish gray coloring which can have a brown to reddish brown cast to it. The stomach is yellow and there is a distinctive black spot at the base of the tail. The top fin is short but high and there are three pairs of barbels. The fins and tail are light and translucent.

These are Hillstream Loaches, meaning they come from cool fast-moving streams. Like other river loaches they are especially designed to cope with living in fast waters. They 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 rocks and driftwood. A moderate amount of plants can be a nice addition.

Hillstream Loaches often enjoy the company of their own kind as well as other community fish. Though generally peaceful with their tank mates some species have been known to nip occasionally. Usually this is just among themselves. It is recommended that they be kept in groups of at least three, with larger groups of five to seven acclimating easier than smaller groups.

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: Traccatichthys
  • Species: pulcher
Rainbow Loach – Quick Aquarium Care
  • Aquarist Experience Level: Intermediate
  • Size of fish – inches: 4.7 inches (11.99 cm)
  • Minimum Tank Size: 30 gal (114 L)
  • Temperament: Semi-aggressive
  • Aquarium Hardiness: Moderately hardy
  • Temperature: 69.0 to 75.0° F (20.6 to 23.9&deg C)
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Habitat: Distribution / Background

The Rainbow Loach Micronemacheilus pulcher (previously: Traccatichthys pulcher, Nemacheilus pulcher) was described by Nichols and Pope in 1927. They are found in China, in the Guangdong Province and Hainan Island. This loach has been recorded from Pearl River drainages of Guangdong, Guangxi Provinces, and Hainan Island in China. Other common names it is know by are Beautiful Hillstream Loach and Mountain Loach.

They are listed on the IUCN Red List, but are widespread and not thought to be declining at a rate to qualify for a threatened category, hence this species is assessed as Least Concern (LC).

This Mountain Loach can be found in streams with smooth sandy bottoms. In nature this loach feeds on crustaceans, insects, larvae, and plant matter.

  • Scientific Name: Traccatichthys pulcher
  • Social Grouping: Solitary
  • IUCN Red List: LC – Least Concern


The Rainbow Loach has a slender, elongated body. It will reach between 4 – 4 3/4 inches (10 – 12 cm) in the wild, though in the aquarium it is usually on the smaller side, and has a life span of 10 years. The top fin is short but high and there are three pairs of barbels.

The coloring can range from very spectacular to rather bland. Its body overall has a greenish gray coloring which can have a brown to reddish brown cast to it. The stomach is yellow and there is a distinctive black spot at the base of the tail. The fins and tail are light and translucent.

  • Size of fish – inches: 4.7 inches (11.99 cm)
  • Lifespan: 10 years

Fish Keeping Difficulty

The Rainbow 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 hardy
  • Aquarist Experience Level: Intermediate

Foods and Feeding

This Beautiful Hillstream 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.

  • 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

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

These fish are mostly bottom dwellers, but will be seen grazing on algae on the sides of the aquarium. Because the Rainbow 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.

It is recommended to have a tank set-up that resembles its natural habitat, slow moving rivers. The substrate should be sandy or small smooth 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. It will appreciate cooler conditions due to country of origin.

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 – Substrate material should be smooth.
  • Lighting Needs: Moderate – normal lighting
  • Temperature: 69.0 to 75.0° F (20.6 to 23.9&deg C)
  • Range ph: 6.5-7.5
  • Hardness Range: 5 – 18 dGH
  • Brackish: No
  • Water Movement: Strong
  • Water Region: Bottom – These fish are mostly bottom dwellers.

Social Behaviors

A good community fish, they will tolerate other tank mates as well as enjoy other members of their own species. They tend to be shy and it is recommended that they be kept in groups of at least three, with larger groups of five to seven acclimating easier than smaller groups.

  • Venomous: No
  • Temperament: Semi-aggressive
  • Compatible with:
    • Same species – conspecifics: Yes – Groups of 5 or more are best. Will ocasionally nip and chase each other, but nothing to be concerned with.
    • Peaceful fish (): Safe – This fish is generally considered peaceful although it will sometimes nip or chase its tankmates. It is best kept in a group of 3-7.
    • Semi-Aggressive (): Monitor
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Threat
    • Safe
    • Shrimps, Crabs, Snails: May be aggressive
    • Plants: Safe

Sex: Sexual differences


Breeding / Reproduction

They are not yet bred commercially.

  • Ease of Breeding: Unknown

Fish Diseases

The Rainbow Loach 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.

Loaches are more susceptible to disease than other aquarium fishes, which may have to do with the faint body scales and no head scales. The most common disease that this loach 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 loaches are often the first to be attacked. Take great care in treating ick as loaches are very sensitive to the medications used to treat it. Often the dose is half of what is normally used.

The second most common thing that affects loaches is something called skinny disease. This can be diagnosed fairly easily. If your loaches are eating a nutritious diet and in healthy amounts,  and still seem to be loosing weight, there is a good chance they have skinny disease. This idisease is caused by internal parasites and can be treated with medication if used carefully.

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 Beautiful Hillstream 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 Rainbow Loach is occasionally available.