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Dwarf Chain Loach (Ambastaia sidthimunki)

Ambastaia sidthimunki
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Family: Botiidae

Northern Thailand. A. sidthimunki appears to be restricted to the Mae Klong river basin in western Thailand and the Ataran (Kasat in Thai) drainage, around the border between Thailand and Myanmar (K. Udomritthiruj, pers. comm.). Though potentially endangered it is still found in both systems, but Thai localities are kept secret for conservation purposes.

The Ataran basin depict relatively slow-flowing sections of forested, seemingly well-oxygenated headwaters with clear water, a mixed sand and rock substrate plus lots of submerged driftwood and leaf litter.

Maximum Standard Length:
50 – 60 mm.

Aquarium Size:
For long-term maintenance an aquarium with base measurements of 80 x 30 cm or equivalent should be the smallest considered. It is advised to find a filter which has a water flow between 4-5 times the volume of your aquarium.

All botiids require a well-structured set-up although choice of decor is more or less down to personal taste, with A. sidthimunki one of the few representatives suitable for the fully planted aquarium due to its diminutive size and tendency to swim above from the substrate. A natural style arrangement could include a substrate of sand or fine gravel alongside smooth, water worn rocks and pebbles, driftwood roots and branches. Lighting can be relatively subdued, and plants able to grow in such conditions such as Microsorum, Taxiphyllum, or Anubias spp. can be added. These have an added benefit as they may be attached to pieces of decor in such a way as to provide useful shade.

Be sure to provide plenty of cover as A. sidthimunki are inquisitive and seems to enjoy exploring their surroundings. Rocks, wood, flower pots and aquarium ornaments can be used in whichever combination to achieve the desired effect, and this may also help reduce aggressive behaviour. Bear inmind that these fishes like to squeeze themselves into small gaps and crevices, meaning items with sharp edges should be omitted, and any gaps or holes small enough for a fish to become trapped should be filled in with aquarium-grade silicone sealant. A tightly fitting cover is also essential.

Although botiid loaches do not require turbulent conditions they prefer well-oxygenated water with some flow, are intolerant to accumulation of organic wastes, and requires spotless water in order to thrive. For these reasons they should never be introduced to biologically immature set-ups, and adapt most readily to stable, mature aquaria. In terms of maintenance, weekly water changes of 30-50% tank volume should be considered routine.

Water Conditions:
Temperature: 20 – 30 °C
pH: 5.5 – 7.5
Hardness: 18 – 215 ppm

Although A. sidthimunki appear to be chiefly carnivorous they will also eat vegetative matter if available, often including soft-leaved aquatic plants. They are largely unfussy feeders but should be offered a varied diet comprising quality dried products, live or frozen chironomid larvae (bloodworm), Tubifex, Daphnia, Artemia, etc., plus fresh fruit and vegetables such as cucumber, melon, blanched spinach, or courgette. Home-made foods using a mixture of natural ingredients and bound with gelatin are also highly recommended. Chopped earthworm can provide a useful source of protein but should be used sparingly, and although most botiid loaches prey on aquatic snails to an extent they are not obligate molluscivores and should never be considered as ‘pest control’. Once settled into an aquarium they are bold feeders and often rise into midwater at meal times.

Behaviour and Compatibility:
This species is generally considered to be an excellent choice for the community aquarium, but caution should possibly be exercised since conflicting observations exist. While some aquarists consider it to be peaceful over the long term others report the opposite, with sedentary or long-finned fishes most at risk. Typical injuries supposedly involve missing eyes or chunks of finnage, but it is unclear why this occurs in some cases and not others, and genuine proof remains lacking. It is therefore difficult to make recommendations; at the least we suggest that this species is unsuitable for smaller aquaria and should be maintained in as large a group as possible. A. sidthimunki are gregarious and appear to form complex social hierarchies. They should be maintained in groups of at least 5 or 6 specimens, preferably 10 or more. When kept singly they can become withdrawn or aggressive towards similarly shaped fishes, and if only a pair or trio are purchased the dominant individual may stress the other(s) to the extent that they stop feeding. That said, they seemingly require regular contact with conspecifics, and this is exemplified by a number of behavioural rituals which have been recorded consistently in aquaria.

Sexual Dimorphism:
Sexually mature females are normally fuller bodied and grow a little larger than males, while adult males develop slightly elongated snouts plus noticeably fleshy, thickened lips.

A. sidthimunki is farmed commercially for the aquarium hobby via the use of hormones but reports of breeding by private aquarists are more or less unheard of, possible because the majority are seasonal, migratory spawners in the wild. While controlled breeding in the absence of chemical  stimulation remains elusive, some instances of young fish appearing in established aquaria have occurred, with a particularly notable example being that of UK loach expert Mark Duffill who discovered a number of juveniles among his group of 36 adult specimens in 2007. The fish were fed a varied diet as suggested above, pH was around neutral and the fish were housed in a 284 litre aquarium alongside groups of various small cyprinids and other loaches.

It has been observed in aquaria with both high and low water flow and seems to be habitual to the extent whereby some individuals will shadow other fishes if no conspecifics are present.

Sound also appears to be an important factor in communication since these loaches are able to produce audible clicking sounds, these increasing in volume when the fish are excited. The behavioural aspects of this phenomenon remain largely unstudied but the sounds are thought to be produced by grinding of the pharyngeal (throat) teeth or subocular spines. A further curiosity is the so-called ‘loachy dance’ which involves an entire group swimming in a constant, restless fashion around the sides of the aquarium, usually utilizing the full length and height. Botiids also often settle at peculiar angles, wedged vertically or sideways between items of decor, or even lying flat on the substrate. This is no cause for alarm and appears to be a natural resting behaviour.

Ambastaia spp. also possess sharp, motile, sub-ocular spines which are normally concealed within a pouch of skin but erected when an individual is stressed, e.g., if removed from the water. Care is therefore necessary, since these can become entangled in aquarium nets and those of larger specimens can break human skin. Botiids are also susceptible to a condition commonly referred to as ‘skinny disease’ and characterized by a loss of weight. This is especially common in newly-imported specimens and is thought to be caused by infestation of parasitic nematode roundworms. It is treatable using proprietary anthelmintic medications such as Flubendazole or Levamisole.