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| For The Love of Loaches |
| 15/06/2007 |
Loaches are among the most popular aquarium fish and have been for many years. At first glance this might seem rather odd; after all, these fish are primarily nocturnal, and many species like to hide away out of sight during the day. Some get rather large, others are distinctly waspish in temperament, and most are sensitive to poor water quality, making them less than ideal choices for the inexperienced aquarist.
But loaches do have a positive side. They are personality fish for a start, adding character to the community aquarium. Swimming about at the bottom of the tank foraging for food they contrast nicely with midwater fish like barbs and cichlids and make an excellent alternative to catfish. Though they may be shy at first, when kept in sufficient numbers and allowed to settle in, loaches can become much more trusting and eventually become active during the day, especially at feeding time. Once swimming about in the open, these sociable fish are often rather comical in their level of activity, jostling for position in the hierarchy and at times producing audible clicking noises as they communicate to one another. Many loaches are also rather beautiful fish. The clown loach is of course the champion here, having colours that rival those of any coral reef fish, but there's also the strikingly marked dwarf loach and the comical kuhlii loach, among others. Best of all, there's lots of variety to choose from, with new species appearing in the trade on a regular basis. Some of these are traded even before they receive formal scientific names!
Biology
The loach family, the Cobitidae, is closely related to carp family, the Cyprinidae and their overall morphology is very similar. Like carps and catfish, loaches possess a set of bones known as Weberian ossicles that connect the ears to the swim bladder. These bones allows the swim bladder to act as a "sound box", a structure that amplifies sounds and so allows loaches and carps to have a much better sense of hearing that most other fishes. As well as a keen auditory sense, loaches are equipped with a number of sets of barbels around the mouth with which they can locate prey by taste and touch. Most loaches forage on the substrate, using the barbels to hunt for small invertebrates such as insect larvae and worms that may be hidden in the sand. One peculiarity of loaches is the possession of retractable spines just below the eyes, apparently used for defence (a nasty surprise for any predatory fish or bird that tries to swallow a loach!).
Only one loach is found in North Africa (specifically, Morocco) while 33 are known from Europe. The UK is home to only a single native species of loach, Cobitis taenia. No less than 170 species have been found in Asia, in both tropical and temperate zone waters. With a few exceptions, loaches are freshwater fish that prefer clean, fast-flowing streams with lots of water movement and plenty of oxygen. Some species are also found in brackish water environments, such as the horseface loach Acantopsis choirorhynchos but the majority of loaches are intolerant of brackish water. Most species are nocturnal or at least retiring, staying hidden under rocks or burrowed into the sand except when foraging.
In terms of size, loaches tend to be fairly small, with most species in the 5-15 cm size range. Of the species offered for sale, the smallest loaches are things like the dwarf loach Yasuhikotakia sidthimunki, at around 5.5 cm when fully grown, and the worm-like kuhli loaches such as Pangio kuhlii that may reach 10-12 cm when mature but remains very slender and so easily housed in even modest aquaria. At the other end of the size range is the clown loach Chromobotia macracanthus that may be sold as delightful 5 cm tiddlers but will eventually reach a whopping 30 cm! The biggest loaches known are Leptobotia elongata and Lepidocephalichthys manipurensis, both around 50 cm long, though neither of these is commonly traded.
Very few loaches have ever been bred in captivity, and none spawn regularly in home aquaria. Observations of fish in the wild suggest that they are all egg layers, typically scattering the eggs on the substrate and offering no broodcare at all.
What's in a name
Until fairly recently, loach taxonomy was pretty straightforward. At least as far as the aquarist was concerned, of the species offered for sale the kuhli loaches were all placed in the genus Acanthophthalmus, horseface loaches in the genus Acantopsis, weather loaches in the genus Misgurnus, and almost everything else in the genus Botia. However, within the last decade or so loach taxonomy has been substantially revised as the diversity of the group was better appreciated and the relationships between species became more clear. Kuhli loaches were moved to the genus Pangio, and the genus Botia was divided up into lots of new and more clearly defined genera including Chromobotia for the clown loach, Sinibotia for the coldwater loaches of China, Syncrossus for the big riverine loaches like the tiger loach, and Yasuhikotakia, for the small Southeast Asian loaches such as the skunk and dwarf loaches.
Basic care
Most loaches inhabit clean, very clear waters. Of the species regularly offered for sale, only the weather loach and the kuhlii loach can really be considered "hardy" in the sense of doing well where water quality is less than perfect. With all the other commonly traded species, excellent water quality is a prerequisite. Water chemistry, on the other hand, is not so important, any anything suitable for tropical fish generally will suit most loaches perfectly well.
Loaches are all essentially opportunistic predators, feeding primarily on infaunal invertebrates such as worms, crustaceans, insect larvae, and snails. While they certainly will "scavenge" to some degree, eating leftover flake food and anything else they can find, no loach should be expected to survive on such scraps alone. Frozen bloodworms and tubifex are an especial favourite, while many of the larger species seem to enjoy small snails. As a staple diet, catfish pellets and tablets work extremely well. At least to begin with, food should be offered at night.
As far as social behaviour goes, loaches have tended to be misunderstood. Most species are more or less schooling fish, and do best kept in groups. Kuhlii loaches in particular will simply hide away unless kept in a fair sized group. Half a dozen specimens is really the minimum number in most cases. When kept singly or in too-small a group, some loaches, particular those referred to as "botias", can become aggressive.
Loaches are peculiarly sensitive to whitespot, particularly when stressed by poor water quality, insufficient oxygen levels, or by being kept in too-small a group. Otherwise, loaches are generally low maintenance animals provided their needs are met, and many species, such as the clown loach, gave life spans measured in decades.
Old favourites
One of the most regularly traded loaches is the horseface loach Acantopsis choirorhynchos. This excellent species gets to around 20 cm in aquaria and needs to be kept in a tank with a sandy substrate so that it can dig itself in. This species will spend much of the time buried under the sand with just its head poking out. Almost eel-like in shape, as its name suggests it also has a long, surprisingly equine head and alert, expressive eyes. It feeds by taking in mouthfuls of sand and filtering out food particles with its gills. Horseface loaches are peaceful and can be kept either singly or in groups. A first-rate choice for tanks containing large but non-aggressive species like barbs, angelfish, gouramis, and so on. Be sure to distinguish this species from the long-face loach Acantopsis octoactinotos, a species that is superficially similar in appearance but tends to be more aggressive and territorial.
One of the few botias to remain in the genus Botia, Botia lohachata has been sold under a variety of common names including Pakistani loach and yo-yo loach. As with most other botias, this species is gregarious but boisterous, and while it should be kept in groups of six or more, these fish are somewhat feisty among themselves, and shouldn't be overcrowded. Providing them with plenty of swimming space as well as lots of hiding places is important. These are very attractive fish, with a silvery body bearing a complex pattern of brown squiggles. A good species for the newcomer to loaches, these fish reach around 10 cm or so in length.
The superstar of the loach family is unquestionably the clown loach Chromobotia macracanthus. These big (up to 30 cm) and brightly coloured fish are truly show-stoppers, and best of all are among the most peaceful loaches in the trade showing no signs of aggression towards one another or other tankmates. Clown loaches are not difficult to keep, though being bigger than the average loach, a suitably sized aquarium is essential. Clown loaches should always be kept in groups, ideally six specimens or more. Obviously this demands a large aquarium be set aside for them. Admittedly, they grow quite slowly, increasing by three or four centimetres a year, but a school of clown loaches will still need an aquarium around the 300 litre mark to feel at home. One odd characteristic of clown loaches is their tendency to roll onto their sides when resting. This can be rather alarming when first observed, but is actually quite normal.
The weather loach of the aquarium hobby is usually Misgurnus anguillicaudatus, an East Asian species superficially similar to the European weather loach Misgurnus fossilis. Weather loaches are hardy animals, and perhaps uniquely among the loaches in the trade make excellent fish for beginners. They are utterly peaceful, and thrive in both coldwater tanks and subtropical ones, so can be kept with goldfish, in ponds, or in subtropical aquaria alongside things like rosy barbs and peppered catfish. Basic colouration is some sort of speckled brown, but it is very variable. Adults are around 15-20 cm long in aquaria. When kept in groups especially it is delightfully active, in particular making frequent dashes to the surface to take gulps of air. The lining of the intestine absorbs oxygen and then the spent air is passed out through the vent. All in all, these are comical and entertaining fish well worth keeping.
Among the smallest of the loaches are the kuhlii loaches such as Pangio kuhlii. These fish are very eel-like in shape with chocolate brown bands around an orange-pink body. Despite their bright colours, they are rather shy animals, and like nothing better than to hide away inside some cave. Keeping them in a fair sized group in a tank with plenty of plants to produce subdued lighting conditions at the bottom of the tank will help, but even under the best of circumstances these fish tend to remain resolutely nocturnal. At around 8-10 cm long when fully growth kuhlii loaches make excellent fish for the quiet community aquarium, albeit ones that you hardly ever see.
Formerly in the genus Botia and frequently referred to as such by hobbyists given their rather challenging Latin names,Yasuhikotakia morleti and Yasuhikotakia sidthimunki are two old favourites known colloquially as the skunk loach and the dwarf loach respectively. The skunk loach gets to about 8-9 cm in length and has a salmon pink body marked with a black stripe running across the top of the fish from nose to tail. Though widely sold and certainly attractive, it isn't a species for the average community aquarium, being somewhat aggressive even when kept in groups. On the other hand, in a big tank with fast, midwater fish like barbs and silver dollars, these fish can work quite well. The dwarf loach is rather different, being much smaller (less than 6 cm) and completely peaceful. They are intensely sociable fish, and should only ever be kept in a large group. Dwarf loaches are silvery-white in colour with thick dark stripes and bars forming a chain-like pattern along the flanks. A superb fish, but rare in the wild and bred only on a few fish farms, and consequently always expensive. While they enjoy digging in the sand like other loaches, they also swim about in midwater, an unusual habit for a loach.
New friends
The golden zebra or Burmese loach Botia histrionica is a medium sized (around 12 cm) species that does well in a community tank of robust fishes such as barbs and large tetras. Although not commonly traded, it appears to be no more difficult to keep than other botias, and given its moderate size and very attractive colours (brown bands against a silvery-gold body) it makes a nice alternative to the more troublesome but similar sized skunk loach.
The Emperor or Tenasserim River botia is an undescribed species of Botia apparently similar in basic shape and pattern to Botia histrionica but with a much more golden body colour and distinctive orangey markings on the pectoral, pelvic, and caudal fins. A beautiful fish, but not often exported and consequently rather expensive.
The polka-dot loach Botia kubotai is another species of botia worth looking out for. Again it is similar in size and shape to Botia histrionica, but the polka-dot loach can be immediately recognised by their density of the dark brown bands on the body, allowing only a relatively small spots of the pinkish-white underlying colour to show through. The fins are white except for some brown markings. In terms of behaviour they are boisterous but gregarious, and so best suited to communities containing other fairly robust (but not overtly aggressive) fishes.
The river loaches, family Balitoridae
Closely related to the loaches is the family Balitoridae, numbering around 500 species and known colloquially as the river loach family. Included in this family are a few species periodically traded, including the various species of Gastromyzon, typically called hillstream loaches in the hobby. Most are found in Asia, but as with the true loaches, a few species are found in Europe, including one species native to the UK, Barbatula barbatula, and Africa, specifically Nemacheilus abyssinicus.
In terms of basic care, river loaches are very similar to true loaches. They need clean, well oxygenated water with lots of water movement. They are even more sensitive to poor water conditions than true loaches. Most are relatively small, typically 5-10 cm, and tend to be more or less territorial towards one another. The hillstream loaches (subfamily Balitorinae) are peculiarly adapted to feeding on algae and small invertebrates they find attached to rocks, and in aquaria generally need similar foods. The remaining species (the subfamily Nemacheilinae) are essentially loach-like opportunists eating a variety of small prey.
The loach-du-jour at the moment is unquestionably Vaillantella maassi, known in the hobby as the fork-tailed loach. A bizarre animal, it has an eel-like body with a dorsal fin running almost its entire length. The tail fin is long and deeply forked. Colouration is variable, but typically mottled brown with a prominent orange or tan stripe on the dorsal surface running from snout to tail. Fork-tailed loaches are peaceful, rather shy, and generally similar to kuhlii loaches in terms of requirements but seem to be territorial rather than gregarious. Excellent water quality is essential.
Species of Homaloptera are usually traded under the "lizard loach" monicker, a reference to their beautifully camouflaged bodies and ability to cling to objects in a manner reminiscent of geckos. Homaloptera are inhabitants of very fast flowing streams, and use their enlarged pectoral and pelvic fins to create suction that holds them onto rocks and stones even in the strongest current. Maintenance in aquaria depends upon being able to provide these fish with both very clean, highly oxygenated water and as well as a selection of algae and small animal foods such as bloodworms that they will accept. Given the right conditions, these fish are not especially difficult to maintain, but when dumped into the relatively stagnant conditions of the average community tank they fare poorly and tend to be short lived. Homaloptera bilineata, a reddish-brown species that reaches around 10 cm in length, is a typical example.
Closely related to Homaloptera are Beaufortia kweichowensis (the Hong Kong plec, 6-8 cm), and Gastromyzon punctulatus (the spotted hillstream loach, to 6.5 cm), and Sewellia lineolata (butterfly loach, to 4.5 cm). They inhabit identical environments and need similar care.
The genus Nemacheilus yields a variety of species traded periodically, though never commonly. While often attractively marked, these fish tend to be rather belligerent towards one another even though they do poorly when kept singly. Instead, keep in groups but provide them with a spacious aquarium offering lots of hiding places. Nemacheilus masyai is known as the arrow loach or checkerboard loach and reaches at least 12 cm in captivity. Basic colour is off-white below and light grey above, but with a distinctive pattern of square blobs along the flanks and dorsal surface. There is an eye-catching orange and black patch at the front of the dorsal fin. Nemacheilus fasciatus is another species sometimes encountered. Its body is greenish with thick, dark green-brown vertical bands and the tail is red. Maximum size is around 7-8 cm, but because this species is distinctly territorial, do not overcrowd it. A white-tailed variety, possibly a distinct species, is also available.
Allied to the genus Nemacheilus is the genus Schistura, which contains a variety of species that tend to be smaller and less aggressive towards one another. Schistura savona is known as the half-banded loach and stays quite small, around 4 cm, making it a good choice for the home aquarium.
The squirrel loaches of the genus Aborichthys are small (4-8 cm) fish that gained their common name thanks to their large, brightly coloured tail fins. In terms of care they are similar to Nemacheilus. Even smaller is Barbucca diabolica, a species that barely tops 2 cm in length, making it an excellent choice for the smaller aquarium. It has a brown body marked with thin yellow stripes. Again, basic care is similar to Nemacheilus.
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