Cypriniformes
Loaches
Being bottom-dwelling species, the loaches are either eel-like or have a triangular body crosssection, their flat bellies being in contact with the substrate. Loaches may have very small scales covering all the body; be partially scaled, in which case the scales are missing from the underside; or naked. When you think about it, the absence of some or all of the scales is a very sensible arrangement, because if scales were present on the belly of the fish, they would be dislodged as the fish moved over rocks and sharp gravel, leaving it open to infection.
Their distribution ranges across Europe and Asia down to, and including, the Malay archipelago, and also includes the extreme north of Africa (Morocco). The main genera encountered by aquarists are: Acanthopsis, Acanthophthalmus, Botia, Cobitis, Lepidocephalus, Misgurnus, and Nemacheilus. With such a wide range, from the temperate zones down to the tropics, some genera, for example Misgurnus, contain species that are suited to tropical aquaria (for example Misgurnus anguillicaudatus – Chinese Weatherloach) and others (Misgurnus fossilis – European Weatherloach) which should be kept in a coldwater aquarium.
With the exception of some Nemacheilus species, loaches have a bifid (two-pronged) spine beneath the eye, which they can erect and lower at will. These spines are quite sharp and can inflict damage on other fishes as well as becoming entangled in nets. Loaches will often erect the spines when frightened and many a transportation bag has been punctured in this way. To reduce the chances of the fishes being able to puncture the bags make sure that the corners are taped up. A loach will also use its spines to defend its territory: in the aquarium they like to hide away in caves which they defend against other fishes.
The mouth is surrounded by three or four (depending on species) pairs of barbels which are covered with taste receptors, which aid the fishes when they are searching through the substrate for food. In the wild, their diet consists primarily of small worms and insect larvae, but in captivity they will take flake and tablet foods as well as small frozen and live foods and algae. They are also very fond of fish eggs and will try and steal these even if the parents are guarding the eggs.
Many loaches are able to use their intestine to take oxygen from the atmosphere, and so can survive in waters that are low in oxygen. They are also very sensitive to barometric pressure and this may cause them to dash about the aquarium at times. Misgurnus (Weatherloaches) are probably best known for this (hence their common name).
In the aquarium, provide your loaches with a soft substrate. Some, such as Acanthopsis choiorhynchus (horse-faced or longnosed loach) like to burrow under the sand until only their eyes are visible. Caves among rocks and plant roots are also desirable, so that each fish can have a small territory. Most loaches will live in harmony with other fishes, but some, notably Botia berdmorei and Botia lohachata (Pakistani Loach), quarrel amongst themselves and, just to be different, Botia modesta (Orange-finned Loach) picks fights with other fishes, preferring to shoal with its own kind. During these disputes, clicking noises can be heard. It is thought that these may be caused by rapid jerking of the bifid spine in its socket.
The Eotia genus is well represented in the aquarium by species ranging in size from the small Botia sidthimunki (Dwarf Loach, Pygmy Chain Loach) which grows to only about 5 cm (2 in), up to the very impressive 30 cm (12 in) long Botia macracantha (Clown Loach or Tiger Loach). These two species are popular among aquarists, Botia sidthimunki because its size and gentle manner makes it ideal for the community aquarium, even with very small species, and Botia macracantha because of its outstanding coloration.
Botia sidthimunki (Pygmy Chain Loach) is relatively easy to keep and feed in a mature aquarium. They are shoaling fishes and several should be kept together. Unlike the other members of the genus, B. sidthimunki will spend time resting on plant leaves or twigs just above the substrate, or swimming in a shoal in the midwaters of the tank during the day. At feeding time they will greedily take small live foods such as Daphnia and bloodworm as well as flake and tablet foods. A variety of foods and maintenance of good water conditions seem to be the key to keeping these fishes healthy.
Botia macrancantha (Clown Loach) is a much more difficult fish to maintain. Because of its gregarious nature, the keeping of several individuals, as opposed to one or two, is a good start. Their size makes them suited to the large aquarium, but if you can grow them to 15 cm (6 in) or 20 cm (8 in) in captivity you are doing well. If stressed they are susceptible to white spot and any treatments should be used with caution – do not, under any circumstances, exceed the manufacturer’s dosage instructions or the “cure” may prove fatal to your clown loach. Botia macracantha is happy with a temperature in the 25-28°C (77-82°F) range.
Of the slim-bodied species, Acanthophthalmus species (Kuhli Loaches) are very popular. The trouble is, once you put them into the aquarium they disappear into the gravel, under the under-gravel filter plates, even up the intake pipe of external power filters if you forget to replace the strainer. They are, however, ideal for the community aquarium as they cause no problems, but you do need to keep three or four of them if at all possible as single specimens are not so bold. They do come out to forage for food or rest among the plants, but, because of their burrowing habits, are probably one of the worst fishes to catch. They take live, flake, and frozen foods and growth from a skinny boot-lace into a rounded worm-like fish is rapid – an 8-10 cm (3-4 in) fish is a goodsized specimen. These fishes have been bred in captivity: they produce bright green eggs which are stuck to plants near the water surface.
The weather loaches are more seasonal imports and are among the larger loaches. Misgurnus anguillicaudatus can attain 50 cm (20 in) although 20-25 cm (8-10 in) is more usual in the aquarium. It is found from the Amur region of Siberia down through China, Korea, Hainan, and even Japan, and seems to prefer colder conditions, although it will tolerate temperatures up to 25°C, (77°F) for a short time in summer. Typical loaches, much of their time is spent buried in the substrate. Breeding occurs in late spring or early summer. The eggs are laid on plants or fibrous roots and left to fend for themselves.
Coldwater Cypriniformes
Continuing with the loaches, Nemachdlus barbatulus (Stone Loach), Misgurnus fossilis (European Weatherloach), and Cobitis taenia (Spined Loach, Spotted Weatherloach) are ideal for coldwater aquaria. Maintenance is the same as for their tropical cousins except that the temperature should be kept below 20°C (68°F).