Those Underrated Bottom Dwellers

Loaches are popular tank inhabitants in our community aquaria. Many of these bottom dwellers are nocturnal so we may not see them all that frequently and may possibly forget they are even there. In this manner they are generally not well appreciated fish, however they are an important part of any tank. There are seven genera of loaches generally kept in our aquaria: Acanthopsis (long-nosed loach), Pangio (kuhli loach), Botia (clown loach), Cobitis (spotted weather loach), Lepidocephalus (Manchurian loach), Misgurnus (weather loach), and Noemacheilus (European loach). Loaches are generally found in cool and tropical waters of Eurasia though some of the Noemacheilus genus whose native waters drain into Northern Africa, are also found there, one representative as far south as Ethiopia.

Loach anatomy generally reflects their bottom dwelling lifestyles. Their mouths face downwards and are equipped with prominent fleshy barbels that are well equipped with taste receptors. Depending on the species, there may be three to five pairs of these fleshy barbels present. The barbels are used extensively when grubbing through the gravel at the bottom of the tank for goodies.

The eyes of the loaches tend to be small and are frequently covered by a transparent fold of skin, presumably for protection. Most of the loaches lack scales, but when they are present they tend to be small and deeply embedded in the skin, making it difficult to identify them. Body colors vary widely from the bright black and orange bands of the clown loach, the red fins and bluish-gray body of the red-finned loach, to the brownish tones of the weather loach. As well, body shape differs amongst the different genera ranging from the Botia species which have laterally flattened, high-backed, compressed bodies, to the Pangio loaches which have elongated, worm-like bodies. Most species of loaches live in the fast running waters of streams and rivers so they have developed strong vertical fins, especially the pectoral fins. Due to their bottom-dwelling habit, they tend to have under-developed swim bladders which makes it easier for them to remain on the bottom in these fast waters. Interestingly, some species of loaches are able to gulp atmospheric air which they keep in their intestine to use as a secondary respiratory organ. Misgurnus fossilis is one loach capable of doing this and so can live in poorly oxygenated waters. All loaches possess very sharp, bony spines behind their eyes that they can unfold and use to warn off other fish (and the occasional fish keeper who insists on taking them to shows).

Loaches are easy fish to keep in the aquarium. Some (such as the weather loach) come from colder waters throughout Europe and so do better in tanks that are kept below 24C, whereas those loaches (such as the Pangio and Botia species) come from tropical Asia, and do better in temperatures above 24C. We know of one club member who keeps his weather loach in his pond during the summer where it is most effective in cleaning up algae and insect larvae. Consequently, when acquiring loaches it is best to research their temperature requirements first. Other than temperature, loaches are very tolerant of most tank conditions. Most appreciate slightly alkaline, clean water with lots of plants and places to hide. Hardness and pH do not seem to be important factors with these fish. The worm-like loaches appreciate a fine-graveled bottom as they tend to burrow into it. This often makes them a difficult fish to show as they dive for cover the minute the judges come by!

Feeding is not much of a problem as loaches will eat anything and everything. Flake, shrimp and Spirulina pellets, live foods, frozen foods, and tubifex worms (freeze-dried) are all accepted eagerly. However, like catfish, loaches should not be left to pick up only scraps from the bottom. Sinking food should be included in daily feedings. The Botia species have a special fondness for snails and will rid your tank of any snails very quickly. As well, raw or boiled zucchini (boiling the zucchini causes it to sink) is also received and devoured with great relish. You can almost see the rapture on their faces when these delicacies are placed in the tank. Most of the time it is a fight between the plecos and the loaches to see who gets the most zucchini. Weather loaches will literally turn inside out if offered tubifex worms, live or freeze-dried. We never see our weather loach eat but when the tubifex worms come out he will eat right out of your fingers. It does not take him long to sense the presence of tubifex in the water.

Spawning of loaches has met with varying degrees of success. Misgurnus fossilis, Cobitis taenia taenia, Pangio kuhli, and Botia macracantha have been successfully spawned in captivity though with great difficulty. All others have yet to be spawned successfully.

We keep four types of loaches: Botia sidthimunki, Botia macracantha, Botia morleti, and Misgurnus fossilis. Our favorite loach of all is the clown loach. One of the first fishes we purchased when we started our first aquarium was a trio of clown loaches. These loaches can be quite expensive (more so then other Botia species) possibly due to a depletion of wild stock and because they are fairly slow growing. Clowns tend to be very susceptible to ick as over the years we have had to treat our clowns several times for this ailment. Consequently, this is one of the loaches that requires warmer temperatures. They are very attractive with broad bright orange and black vertical bands, and are one of the most colorful of freshwater fishes. We have several age-groups of clowns as I can not resist the babies that come in every year in the late fall. Clown loaches are best kept in groups of three or more as they will do poorly if kept alone. Our largest is approximately 15cm long and is a male, while the smallest is barely over 2 cm. We purchased Bozo (the big guy) when he was only 3 cm or so, so in five years he has grown fairly quickly for a loach. Adult clown loaches can achieve a size of 30 cm in the wild but rarely more than 18 cm in the aquarium. The large clowns are considered tasty eating in their native lands. The best way to sex these fish is to observe their tail shapes. Females have straight tips while the male’s tips curve inwards (see illustration, from Baensch, 1991). They prefer warmer temperatures and tanks that are very well planted with lots of hiding places. To encourage these loaches to be more active during the day, subdued lighting is generally effective.

These loaches can be quite entertaining, displaying lots of personality. Our three largest occupy a 200-liter community tank and are always bulldozing their way through the other inhabitants while grubbing around. Clowns have an unnerving habit of lying on their sides almost as if to sleep. The first time we saw this we thought the fish had died, or was well on its way, it lay so still. However, approaching the tank always made the fish zip off as if you had just interrupted a well deserved afternoon siesta. Wouldn’t it be a fascinating sight to see whole schools of these fish in their native waters all lying on their sides taking a quick zizz? Another interesting habit of clowns (and other Botia) is the clicking noises they make. These sounds are used when squirmishes occur amongst tank mates or when they are warning other tank mates away. These clicking sounds are quite loud and can be heard all over the house.

Clown loaches have been successfully bred in the home aquaria but usually only by accident. Reports of greater success in spawning clown loaches with injections of pituitary gonadotropic hormones has come out of the Orient. All successful spawnings seem to have occurred with large, adult fish. In the wild these loaches spawn during the rainy season in foamy, fast running, spring-fed waters in Indonesia, Sumatra, and Borneo. The fry grow up in slower or standing waters in the lower estuaries of these streams.

Our small school of Botia sidthimunki are always a delight to watch. This dwarf loach only reaches an adult length of 5.5 cm and is the smallest of all the loaches. It is a peaceful, schooling, lively little fish that is very active during the day. These fish have interesting markings with dark lateral and dorsal bands interspersed with circular spots separated by dark to light gray vertical bands on the upper half of the body. The lower half of the body is cream to white. Dark spots may or may not be present on the caudal fin. Our school of four makes quite a sight dashing about the bottom of a 120-liter community tank. We’ve nicknamed them “the weasels” as they remind us of the weasels in the movie “Who Framed Roger Rabbit?”, always erratically zinging about as if a few bricks short of a full load.

These little loaches hail from small, muddy lakes in northern India and Thailand and thus prefer warmer temperatures, 26C to 28C though ours do well at 24C. The tank bottom should be covered with fine gravel and a layer of mulm to keep the dwarves happy. Lots of plants, rocks, and caves for hiding places are also preferred. All community tanks should include a school of dwarf loaches!

Botia morleti, commonly called Hora’s loach or the skunk loach, is a slightly more aggressive loach than other Botia species. We keep three in a tank with two pairs of South American cichlids (Herichthys ellioti and Geophagus steindachneri) and armored catfish where they get along fine. We have heard reports of these loaches being too aggressive and destructive for other smaller tank mates. This has not been our experience as our three were kept with Apistogramma, tetras, and barbs with no problems. The literature states that B. morleti are nocturnal but ours seem to be busy all day. They obviously have not read the books! They are poorer than average swimmers and seem to launch themselves off the bottom for short distances before falling back to Terra Firma.

Skunks are quite attractive. They have fawn-colored, smooth, scaleless bodies with a black stripe that runs along their back from the tip of their nose to the base of the tail where it curves down laterally. Small black spots may be present in the caudal fin. They inhabit the waters of northern India and Thailand and actually prefer slightly acid, soft water, though ours seem to have done well in our hard, alkaline water. Baensch states it is impossible to sex these fish. However, of our three one is incredibly plump and broad whereas the other two are noticeably skinnier. We surmise that the fat one is probably a female. We find these loaches quite entertaining as they seem to do more clicking than our other loaches and are very active. This is a species we would recommend for more active tanks.

Our weather loach (Misgurnus fossilis) came to us from a club auction where we picked him up for the princely sum of $1. The most interesting thing about these long, brownish, eel-like loaches is their response to pressure changes brought about by weather systems. With pressure changes these fish become very agitated and swim energetically around their tanks. In Cochrane, pressure changes are daily occurrences so in our tank our weather loach is quite active. Despite their size, up to 30 cm, these loaches are peaceful sedentary fish that are more active at night. The barbels of this fish look like a frill around the mouth, giving it a rather comical appearance. They like to dig in the gravel so fine gravel is preferred. However, ours rarely disturbs any plants. Like other loaches, weather loaches prefer well-planted tanks with lots of rocks and caves for hiding spots. This is one species that has been successfully spawned in captivity. In between sinuous movements the eggs are usually deposited on plant leaves. The spawning season runs from April to July, coinciding with spring rains in the cooler waters of European rivers. While not the most attractive of the loaches, the weather loach seems to have been left over from a more prehistoric time making it an interesting specimen for any community tank.

While this has been a general overview of those fish commonly known as loaches, we hope it will encourage aquarists to try and keep more loaches. Many are attractively colored or patterned and all are certainly entertaining and interesting aquarium inhabitants. Have you had your loach today?


Baensch, H & Riehl, R. (1991). Aquarium Atlas. Melle, W. Germany.

Loiselle, P. & Pool, D. (1993). Hobbyist Guide to Catfish and Loaches. Tetra Press, Blacksburg, Virginia. ?