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Clown Loach (Chromobotia macracanthus)

Chromobotia macracanthus
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Family: Botiidae

Native to the Greater Sunda Islands of Borneo and Sumatra

Mostly inhabits main river channels but migrates upstream into smaller tributaries to spawn during the wet season, when some areas become temporarily flooded. The fish are therefore found in different habitat-types depending on the time of year, and the habitats themselves also vary; water flow and depth tend to increase significantly during the wet season, for example. Turbidity and pH typically also rise during this time while water temperature drops. Age also plays a part, with juveniles remaining in the flood plain breeding grounds for several months whereas the adults typically return to the main rivers post-spawning with very old individuals probably not migrating at all. The majority of its native rivers contain soft, tea coloured water and pass through areas of rainforest, although much of what once existed has now been degraded. In the floodplain swamp forests marginal vegetation is normally thick with shade provided by the forest canopy above. Substrate consists largely of detritus and leaf litter with submerged tree roots, trunks, patches of previously emerse vegetation, while the water tends to be almost still.

Maximum Standard Length:
Supposedly exceeds 400 mm but reports from its native rivers suggest an average adult size between 200 – 305 mm, borne out by the largest aquarium specimens we know of. It’s possible that very old female individuals might grow bigger but this is likely to take a long time since growth tends to slow down considerably once the fish reach 150 – 200 mm.

Aquarium Size:
A tank with base measurements of 180 x 60 cm or equivalent is the absolute minimum required to house a group, and young specimens should only be grown on in smaller aquaria if several partial water changes are conducted each week.

All botiids require a well-structured set-up although choice of decor is more or less down to personal taste, with Chromobotia macracanthus 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 Chromobotia macracanthus 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 in mind 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: 24 – 30 °C
pH: 5.0 – 7.0
Hardness: 18 – 215 ppm

Although Chromobotia macracanthus 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 mid water at meal times.

Behaviour and Compatibility:
Not especially aggressive but don’t keep it with much smaller fishes as they may be intimidated by its size and sometimes very active behaviour. Slow-moving, long-finned species such as ornamental bettas, guppies and many cichlids should also be avoided as trailing fins can be nipped. More suitable tankmates include peaceful, open water-dwelling cyprinids, while in larger tanks members of Barilius, Luciosoma, Balantiocheilos and Barbonymus become options.

Sexual Dimorphism:
Adult females are normally fuller-bodies and larger than comparably-aged males. Some theories suggest that males also possess a more deeply forked caudal fin but this is unproven as far as we know.

In nature this species is a migratory spawner, moving from the main river channels into smaller tributaries with surrounding, temporarily inundated flood plains during the rainy season. These movements usually begin in September with spawning typically occurring in late September/early October, though the timing of this is beginning to shift with the changing climate (Evers, 2009). The eggs drift and come to settle in the riparian vegetation and there the initially pelagic larvae spend their early days feeding on micro-organisms. Some drift too far, enter the main rivers and are eventually swept out to sea, and modern-day native fishermen have come to take advantage of this phenomenon (see ‘notes’). The remaining fry stay in the flooded areas until the waters begin to recede at which point they typically measure around 30mm. They then move into the smaller tributaries until large enough to complete their passage into the major channels where they remain until sexually mature and able to undertake spawning migrations of their own.