The Red-Tailed Squirrel Loach

Author: Roland Schreiber

A rarely imported loach, the red-tailed squirrel loach is worthy of its own setup dedicated to its exacting need for cold, swift-moving water.

A Century of Loaches

Almost exactly 100 years ago, during an expedition to the Indian Abor-Hills, a loach that displayed rather curious body markings was captured. It was obvious, after some research, that this new species represented a completely unknown genus.

The Abor-Hills are among the most desolate places and one of the most beautiful areas on earth. The hills can be found in Arunachal-Pradesh, a state in northeast India that borders Bhutan, the People's Republic of China (Tibet), and Myanmar. On the north side, the gigantic flank of the Himalayas is connected.

Due to its remote area of origin, this genus, Aborichthys, contained only five valid species until now, often introduced to the trade as bycatch or a misidentification of other well-known loaches. Nearly all Aborichthys species are threatened in their natural habitat. Due to soil erosion, caused by deforestation, their habitat is in danger and needs protecting. The areas where the loaches are found in Darjeeling, the hill streams, are polluted due to agricultural runoff, the widespread use of poison, and electrical fishing.

Aborichthys species mostly inhabit shallow, swiftly flowing stretches of streams and minor rivers, often with a noticeable gradient. Not only are they rheophilic (needing fast-flowing water), but they also inhabit rushing torrents with flow velocities from 16 to 65 feet per second!

A. elongatus

The red-tailed squirrel loach (A. elongatus), is native to the entire Arunachal Pradesh and the district of Darjeeling, situated in the northernmost part of the state of West Bengal, India, and widely known to passionate tea lovers. Here, in the Reang River at an altitude of 2,000 feet, the specimens were found.

This small species, also colloquially known as the red-tailed or stripedsand loach, reaches a maximum length of 4 inches and, because of its distinct social behavior, is a very interesting and peaceful ornamental fish, even for small-sized aquaria.

A. elongatus is found in tropical rainforests with temperate climate and heavy monsoon rains during the rainy season (July to September). The landscape is marked by alpine conditions in the cold, high mountain regions, with mountain peaks reaching approximately 19,000 to 23,000 feet, as well as ice-cold, rushing mountain streams at an altitude of 13,000 feet. The need for cold water must be replicated in the aquarium.

This species lives in caves formed by the gravel and rock substrates. The red-tailed loach is optimally adapted to this life by an extremely elongated body and a large, paddle-like caudal fin. In addition to this, the species possesses adhesive organs at the inferior side of the outer pectoral and pelvic fin rays.

There are numerous local variants of the red-tailed loach. It is not clear whether these variants are different color morphs of the same species or represent different species. But, in principle, the marking on the rounded caudal fin is characteristic of all Aborichthys species. Due to the remote nature of its natural waters, this species is seldom seen in the trade.

Uncommon Find, Easy to Keep

At the end of the year 2011, I happened to get some of these rare river loaches from an ornamental fish importer in Germany. My specimens didn’t require much maintenance. The animals should be kept at least in small groups with more than five specimens because of their highly developed social behavior. I set up a 21-gallon tank for them, using stone slabs to recreate their natural habitat.


For the substrate, I used a mixture of a few medium-sized pebbles with small gravel and fine sand between. Since Aborichthys species like to dig, decorative items are best placed directly onto the aquarium base before the substrate is added. I always try to imitate the natural environment of fishes (water chemistry values, filtration, light, substrate, etc.) as closely as possible. Aquatic plants are not a necessary feature, though you can use them in order to enhance the aesthetics. For this reason, you can do without lightning.

Tank Requirements

At the beginning, I installed a simple 265-gallon-per-hour external filter for my river loaches. Recreating the strong current and oxygen-rich water was more important than the filtration because I conducted regular water changes. I used normal tap water with a conductivity of about 650 µS/cm (water hardness about 3.5 mmol/l). The pH value was correspondingly high at 7.3. The water temperature was nearly 77 ̊ F at the beginning. Vuorela (2007) caught A. elongatus in spring 2004 in the Reli River where the water temperature stays below 68 ̊ F and there is a high pH value of 8.2.

Water Requirements

It is often observed that the temperatures fall below 50 ̊ F during winter. Despite the fact that these species are found in warm waters, up to 79 ̊ F, during the hottest time of the year, this high temperature should be used only for a relatively short period of time. After I noticed accelerated respiration in the loaches above a temperature of 77 ̊ F, I switched off the aquarium heater immediately. The water temperature plummeted to an average of approximately 64 ̊ to 68 ̊ F. The loaches really enjoyed this change, as they became active swimmers and appeared to be in good health.

Breeding Loaches

The small Asian loaches can be induced to breed by two simple things: feeding and water changes. It can be confidently said that A. elongatus is omnivorous. The loaches are interested in everything that swims, floats, sinks, or lies on the substrate. It just has to look like food. The curious loaches are always searching for anything to eat and are not afraid to snatch dried food, even at the water’s surface. Worms hidden in the substrate are excavated purposefully by the use of their snout. Furthermore, the daily feeding with live Artemia salina was a true pleasure to my loaches. As soon as I tipped a small sieve full of the brine shrimp nauplii into the water, the loaches were excited. They spent the next hour tirelessly capturing the tiny crustaceans.

The weekly water change really excited the river loaches. As soon as I added fresh water into the tank, all the loaches lined up close together, even if they were hidden between the layers of stone slabs before.


Breeding loaches can be considered difficult. Aquarists are still discovering how to breed them, although a few ambitious fish lovers have achieved new knowledge and advances in this specialized area.

The issues of sexual differentiation, seasonality, as well as the reproductive cycle of the specimens in their natural habitat (e.g., spawning migration) are still a wide-open field of research for inquisitive aquarists. I found no reports of successful breeding of Aborichthys in literature.

My Experiment

A few members of the sucker loach family live in fast-flowing freshwater mountain streams and are known to migrate upstream into cold and oxygen-rich waters during the spawning season. I wanted to perform a most extraordinary experiment. I replaced my standard aquarium (21 gallons) with a large, elongated “race tank” (nearly double the volume). The “tiny” external filter was supplemented by a forceful powerhead (1,000 gallon/hour). I placed a small foam cartridge at the inlet of this filter to prevent the agile loaches from being sucked into the pump. Furthermore, I sealed the aquarium cover meticulously because the Aborichthys species are known to locate even the smallest gap.

My red-tailed loaches obviously enjoyed their new surrounding very much. They especially loved to play in the oxygen-rich jet of water produced by the powerhead. I was amazed how much power the loaches have to struggle against the strong and steady flow of water.

I fed only small living food (mainly water fleas, Artemia salina nauplii, mosquito larvae, and Cyclops) during the last weeks.

Reducing the Temperature

After another ten days, I reduced the temperature. Since the aquarium heater was already removed, I cooled down the tap water for the water change by using ice cubes. I used an external 21-gallon vat to lower the tap water temperature to 45 ̊ F by adding the frozen ice. From there, I pumped the ice-cold water directly to the aquarium with the aid of a small water pump. In this way the small loaches benefitted from a weekly “ice-cold” shower, which they obviously enjoyed much. The water temperature in the aquarium decreased for a short period of time to between 55 ̊ and 59 ̊ F and then settled at a room-temperature level between 64 ̊ and 68 ̊ F within 24 hours. Needless to say, my beloved water plants disliked this procedure; they died within a short period of time.

New Characteristics

After a few weeks and a lot of water changes, one of the seven specimens (a female?) displayed some significantly different characteristics: It was now colored in a paler tone (and a little bit yellowish) compared to the other six olive-gray specimens. It also clearly exhibited a more chubby girth, and the striped pattern on the body disappeared nearly completely.

Two of the loaches, the yellowish one and a grayish one, separated themselves from the others distinctly and stayed very close to each other for most of the day. The darker Aborichthys was the active one. It nudged the brighter loach with its snout and pestered this fish for a long period of time. They often rested close to each other on a stone slab, and sometimes their bodies trembled. Contrary to the behavior often observed in other loaches, like parallel swimming or bashing with their caudal fins, this was obviously more or less a trembling of the whole body. Sometimes one of the Aborichthys jumped over the other one and continued resting at the other side of his mate.

The other members of the community kept their distance from the two “lovers.” For this reason, I didn’t want to change anything. I continued to offer ice-cold showers once or twice a week and tiny living food.

One day when I came back from work, the two disappeared under a stone slab. The sand underneath was removed and placed on the outside of the cave. My two loaches, still in hiding, were seldom to be seen outside of their hole. They would appear briefly only at feeding times.

No Results

After another week, I became increasingly nervous and impatient and decided to check on the situation. After I removed the whole layer of stone slabs, which I suspected to be a spawning site, there was considerable disappointment. Now it was clear to me that neither eggs nor larvae or juveniles were to be found.

The former brightly colored specimens looked somewhat darker and a little bit slimmer. After I carefully replaced the great mass of stones, they returned to business as usual: hunting brine shrimp and swimming against the strong jet of water. I have found myself wondering whether the loaches eventually spawned and the eggs didn’t develop or maybe the fry were captured by the other specimens.

Maybe the hot-blooded river loaches just had one cold shower too many.