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Family: Botiidae

Common Names: Dwarf Loach, Dwarf Chain Loach

Origin: Chao Phraya and Mekong basins in Thailand, Cambodia and Laos. Found in small streams,ponds and flooded areas.

Compatibility/Temperament: Very peaceful, highly social and interactive so must be kept in a group of at least five. Well suited to a community aquarium of non-aggressive fish. Some sources suggest possible fin nipping of upper fish, but the writer (Byron) who has maintained this species for several years suspects this may only occur with insufficient numbers and/or inappropriate environment.

Dwarf Loach Diet

Omnivore, it readily accepts prepared foods that sink (tablets, pellets); these should be provided, even though it will sometimes take flakes from the surface. Frozen bloodworms and live worms are relished.


Attains 2.5 inches.

Minimum Tank Suggestion

Absolute minimum of 24 inches in length, but a 30 or 36 inch tank is far more preferable; although a small loach, it is an active swimmer.

Water parameters for Dwarf Loach

Soft to moderately hard (to 12 dGH maximum), acidic to slightly basic (pH up to 7.5 but preferably below 7) water, temperature 24-28C/75-82F. Best in soft acidic water.


A smaller "version" of the common Botia-type loaches, and one that is unique in that it shoals above the substrate, often in mid-water, and during daylight. The aquarium should have a substrate of sand or small gravel having no sharp edges, many pieces of bogwood containing tunnels and crevices, caves, and be well planted. A partial layer of dry leaves is appropriate, and this loach will disappear under the leaves in search of food and when "playing." Swimming room is required, for this is an active swimmer. Water flow from the filter should be minimal.

The species was briefly thought to be extinct but is now considered critically endangered in Thailand and is protected; hobby fishes are almost certain to be captive bred, and for years have been spawned with hormone treatments. There is no external sexual characteristics but females are rounder in the body.

This fish is very similar to Ambastaoa nigrolineata but remains smaller at maturity. Like all loaches, it is scaleless and therefore highly intolerant of any medications and chemicals, including salt which will burn the fish. It should never be added to a new aquarium but only to one that is well established. It is intolerant of fluctuating water parameters and conditions. Care should be exercised to ensure the movable spine located under each eye socket [common to all loaches] does not become entangled in a fish net or puncture a plastic bag during transport.

This species was originally described by W. Klausewitz in 1959 and named Botia sidthimunki, the epithet in honour of Aree Sidthimunk, a researcher at the Thai Ministry of Agriculture, Department of Fisheries. In 2004, Maurice Kottelat removed this species from the genus Botia that contains most of the common aquarium loaches and assigned it to the new genus Yasuhikotakia erected by Nalbant in 2002, along with the similar-looking species Y. nigrolineata.

During his comprehensive review of all known loach species that has been in progress for more than 30 years, Dr. Kottelat determined that these two species form a very distinct lineage, and with publication of his paper in 2012 he erected the new genus Ambastaia for these two species. The genus name derives from Ambastai, the name of a river in a work by the first-century writer Claudius Ptolemy, a Greco-Roman citizen in Egypt who lived ca. AD 90-ca. AD 168. During our time this river has been identified as being the Mekong in SE Asia, the natural home of this species. Thus, a most appropriate genus name.


Kottelat, Maurice (2012), "Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei)," Raffles Bulletin of Zoology Supplement 26, pp. 1-199. Available online:

Contributing Members

The following members have contributed to this profile: Byron


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