Gastromyzon

Field observations have revealed that individuals almost always position themselves facing into the flow, either along the sides, behind or under rocks, their specialised morphology (see 'Notes') allowing them to feed and maintain position without being swept away. Not many fishes have been able to successfully colonise this narrow ecological niche, but syntopic species in nature include Gastromyzon extrorsus (Petagas River), G. introrsus, G. lepidogaster (Pad...

G. cornusaccus can be distinguished from congeners by the following combination of characters: secondary rostrum present; incomplete postoral pouch present reduced to pockets located posterior to mouth corners; sublacrymal groove present and visible when viewed laterally; juveniles with thick, cream-coloured bars and blotches on body, adults uniformly-coloured; head dorsum plain; subopercular groove absent; gill slit vertical; snout truncate when viewed dorsally; no scales on abdomen; 55-61 lateral line scale...

One of the more commonly-traded members of the genus and often found in mixed shipments which may contain other Gastromyzon spp. or related fishes like Beaufortia kweichowensis, these often labelled collectively as 'Borneo sucker', 'Hong Kong pleco', 'butterfly loach', etc. It's sometimes misidentified as G. punctulatus, a species not currently traded which possesses yellow finnage and a lighter-coloured, less-intensely spotted body.

This species has probably not been seen in the aquarium trade yet but has been maintained by a few private collectors. It can be distinguished from congeners by the following combination of characters: secondary rostrum present; complete postoral pouch present; body colour brown with up to 9 thin gold stripes; head dorsum dark brown with gold reticulate pattern; subopercular groove absent; gill slit vertical; sublacrymal groove present; sno...

In fact G. farragus and G. ocellatus represent one of 12 pairs of cryptospecies to be found in the genus, differing in subtle aspects of patterning. Cryptospecies are defined as morphologically similar, but reproductively isolated species which in fishes often inhabit adjacent river basins but in some cases occur sympatrically. The phenomenon may be a result of parallel evolution, and is not normally considered to represent an early stage of speciation.

The type locality was a fast-flowing, shallow (50 - 80 cm deep) river between 5-10 metres in width with a substrate of gravel and large rocks. PH was measured at 7.7 and the habitat was unshaded with on...

This species is variable in terms of colour. Large adults may be bright green, orange or barred but are apparently capable of changing from barred to plain in just a few seconds. These different forms have been recorded in the same natural habitats, and some individuals also possess prominent nuptial tubercules covering much of the body.

Field observations have revealed that individuals almost always position themselves facing into the flow, either along the sides, behind or under rocks, their specialised morphology (see 'notes') allowing them to feed and maintain position without being swept away. In nature G. monticola occurs sympatrically alongside Garra borneensis, Osteochilus ingeri, Gastromyzon auronigrus, G. cornusaccus, Nemacheilus olivaceus,...

Some individuals do appear very similar to G. farragus, with noticeable spotting on the head, but can usually still be told apart by examining the caudal-fin which tends to contain only a single thick, dark vertical bar in G. farragus whereas in G. ocellatus there are more often two bars, one thick, one thinner. Intermediate forms do exist though meaning identification is sometimes tricky.

It can be distinguished from congeners by the following combination of characters: gill slit angular; presence of subopercular groove, running continuous to origin of pectoral-fin; body black with numerous, small, evenly-spaced light brown spots; head dorsum black with numerous cream spots; pectoral and pelvic fins with cream spots; caudal-fin with iridescen...

This undescribed species has probably not been seen in the aquarium trade yet but is occasionally maintained private collectors. The 'SK' numbering system used here refers to 'South Kalimantan', home to several unidentified members of the genus. Gastromyzon spp. are placed into various 'species groups' (artificial assemblages of species which may or may not be monophyletic) for ease of reference, and based on colour and patterning G. sp. 'SK01' appears similar to members of the G. ridens group which also includes G. crenastus, G. stellatus and G. zebrinus.

Known only from headwaters of the Sungai (river) Amandit, a tributary of the larger Barito basin in the Meratus mountain range, Kalimantan Selatan (South Kalimantan) province, Indonesian Borneo. There currently exist 36 officially-described members of the genus, all of which are endemic to the island with over half restricted to a single river basin or sub-basin.

Gastromyzon spp. are obligate dwellers of swift, shallow streams containing clear, oxygen-saturated water and have been recorded from sea level to 1350 m amsl throughout hill regions of Borneo. They typically inhabit riffles and runs and are often found above or below cascades and waterfalls. Substrates are generally composed of gravel, rocks, boulders or bedrock carpeted with a rich biofilm formed by algae and other micro-organisms.

For long-term success it's best to provide a mature aquarium with a plentiful supply of algae-covered rocks and other surfaces. If unable to grow sufficient algae in the main tank or you have a community containing numerous herbivorous fishes which consume what's available quickly it may be necessary to maintain a separate tank in which to grow algae on rocks and switch them with those in the main tank on a cyclical basis.

One of the more commonly-traded members of the genus and often found in mixed shipments which may contain other Gastromyzon spp. or related fishes like Beaufortia kweichowensis. These are typically labelled 'Borneo sucker', 'Hong Kong pleco', 'butterfly loach', etc. regardless of species. It's sometimes misidentified as G. punctulatus, a species not currently traded which possesses yellow finnage and a lighter-coloured, less-intensely spo...

Many loaches from the families Nemacheilidae, Balitoridae and Gastromyzontidae are also suitable but research your choices before purchase in order to be sure as some are excessively aggressive or otherwise competitive. Gastromyzon spp. tend to exist in lo...

Much of the natural diet is likely to be composed of benthic algae plus associated micro-organisms which are rasped from solid surfaces. In captivity it will accept good-quality dried foods and meatier items like live or frozen bloodworm but may suffer internal problems if the diet contains excessive protein. Home-made foods usi...