Crossocheilus langei

Aquarium fish: Crossocheilus langei (Crossocheilus langei)
Size: 15 cm
Origin: Asia
Water temperature: 22-26 ° C
Aquarium volume: 200 l

Crossocheilus langei (Crossocheilus langei ) -like algae. Due to its unique ability, it is commonly referred to as a mower among aquarists . Crossocheilus langei is one of the similar species that are sold in Poland as popular “mowers” (abroad, Siamese algea-eater – Siamese algae eater or Siamese flying fox) or Crossocheilus siamensis . Recent work has shown that the name Crossocheilus siamensis is synonymous with Epalzeorhynchos siamensis (Smith 1931), a species described from Tadi Province in southern Thailand, before being transferred to the genus Crossocheilus (Bănărescu 1986). The latter nomenclature is not correct, but is taken as synonymous with Epalzeorhynchos siamensis, which in turn is synonymous with Crossocheilus oblongus, a species described from Java.

C. oblongus is currently assigned to the entire area of ​​Indochina and the Sunda Islands, but despite the vague identity, the nomenclature is routinely ascribed to fish in the aquarium trade. This species has been described as a bluish fish with yellow fins, and is almost certainly not a Siamese large-tailed fish found in aquaristics.


Asia . The species is currently assumed to be found in Borneo, Malaysia, southern and western Thailand, and southern Myanmar.

However, the occurrence of Crossocheilus fish requires further research, as some populations may represent undescribed species. These fish inhabit running waters, streams and tributaries, with sandy, gravelly and rocky bottoms, often in the vicinity of submerged branches and roots of trees. These waters are clear, often shallow, and the sun’s rays can easily penetrate them. This promotes the formation of a rich biofilm on submerged surfaces, which fish are eager to comb through. They are probably found in deeper and murky waters during seasonal migrations.

Characteristics and disposition

A slender gray-brown fish with a characteristic black horizontal stripe. In nature, it reaches up to 15 cm, and usually less in aquarium conditions. On average, he lives about 10 years. Compared to similar species, there is no yellow or red shade. All their fins are transparent or slightly milky.

A characteristic black streak runs from the mouth to the tip of the tail and is unevenly edged in a zigzag. Under stress, the black color can definitely fade away. The lower body is silver white. Top brown, each scale is rimmed, which fully resembles a grid pattern. There is a pair of thin whiskers at the mouth.

A strip is also visible in the young, but the zigzag edge will not be clearly visible until it reaches 5-7 cm in length. Gender very difficult to distinguish.Sexually mature females are generally thicker than males. Members of the genus Crossocheilus are characterized by 8 branched rays of the dorsal fin, fixed maxillary lobes, the absence of a dorsal spine and the fact that the lower and upper lips are not connected, the upper ones are attached to the lower jaw with a thin membrane . Mowers are active and fast fish that feel best in a large group. Under natural conditions, they do not swim in a shoal, but rather in a loose group.

It is recommended to keep 6 or more individuals in the aquarium. When kept singly or in small numbers, they can be shy and skittish, and weaker individuals can be dominated or withdrawn. When kept in larger quantities, they look nicer and show more interesting, natural behavior. They can jump high, so they should not be kept in open aquariums. They often chase each other, but never harm each other.

Peacefully oriented towards other fish, only adults can show territorialism towards their own species and chase away other, smaller fish. They rest in a specific way. They do not lie flat on the stomach, but support the body on the pectoral, abdominal and tail fins. Juveniles rest more often on broad leaves of plants, adults prefer the bottom or dense, low vegetation, eg Cryptocorynes. Their swim bladder is not well developed, so they cannot stay freely in the water, but must be in constant motion.

Nutrition and feeding

In nature, Crossocheilus species feed mainly on algae, diatoms and other phytoplankton and their accompanying microorganisms. In the aquarium, you should avoid feeding with high-protein foods , because fish are not able to metabolize some ingredients efficiently, their regular, long-term consumption may cause excessive fat accumulation and even organ degeneration. The best foods are dry foods with Spirulina, as well as fresh plant foods such as peas, blanched spinach, eggplant, zucchini or chopped fruit. After acclimatization in the aquarium, the fish sometimes swim to the middle parts of the water for food, and often search the rock surfaces covered with biofilm.


They require an aquarium of at least 120 cm in length.

Mowers like ground with the addition of gravel and stones of various sizes. Decorate the tank with roots and plant it with durable plants such as Anubias , Mikrozorium, Bolbitis, which can grow attached to the decoration. Fish feel good in water with strong current . They are characterized by high sensitivity to hypoxia and a high content of nitrates in water. Clean, oxygenated water is important for their breeding, often replaced with fresh water.

Strong lighting is also recommended to stimulate algae growth. The aquarium should be covered to prevent the fish from jumping out. Generally mild and can be kept in the company of many popular species, however, it is best to choose those that also occur in their natural environment, such as Botia rostrata or Crossocheilus reticulatus and fish of the genus Cyclocheilichthys, Devario, Mystacoleucus, Rasbora, Garra, Homaloptera, Lepidocephalichthys , Nemacheil.


It is impossible to reproduce lawnmowers at home . Commercial fish come from harvesting or breeding farms where hormones are used to stimulate spawning.

Real and false mower

There are species in trade that are very similar to the Siamese thicket, but they do not eat algae so eagerly . The characteristics of a real lawn mower are:

  • only two mustaches, not four or no one
  • only one central side band extending to the caudal fin
  • the upper edge of the side strip is finished with a zigzag
  • the scales on the back are clearly dark, edged
  • dorsal fin transparent (in adult fish it may be slightly colored) – do not follow this tip when distinguishing young fish

Differentiation of Crossocheilus species

The distinction between the species commercially available under the name C. siamensis is complex, but there are some differences. C. atrilimes are best identified by the distance between the location of the reproductive organs and the anal fin, which is 38-51 mm (51-89 mm in other species).

A black side band runs from the snout to the tip of the caudal fin; the eye is light brown above the pupil and white below; the jaws are not visible; the lateral line is curved; the fins are light yellow in color. Depending on the mood, this species has the ability to change the appearance of the dark belt, especially during duels it becomes wider and fades away. Generalizing the characteristics, in C. langei the eye is reddish-gold above the pupil and white below; has two pairs of mustaches; the lateral line is generally straight and passes through the center of the dark belt; the fins are brownish. Although the dark stripe also becomes light during duels, it does not change width, in addition, there is a dark spot on the underside of the body directly in front of the anal fin.

Most often, it is this fish that is referred to in the literature and the Internet as Siamese algae eater , but as there are slight discrepancies in the descriptions, undescribed species should also be taken into account. Another fish in this group is an undescribed species (sometimes described as C. sp. Citripinnis ). It is a larger fish growing up to 150 mm standard length, with a pair of jaw whiskers visible.

The fins are lemon yellow, especially intense in older animals. The dark stripe does not change width or color, the lateral line is curved and the overall shape of the body is similar to that of C. atrilmes, therefore both species can be easily confused at a young age. There may also be other undescribed Thai-origin species marketed as C. siamensis , but so far no detailed work has been done on this.

In 2009, Tan and Kottelata described a new species, C. obscurus , from the Hari River (Batang Hari) in Sumatra. This species is also relatively large, it grows up to approx. 142 mm in length and is described as follows: one pair of anterior maxillary whiskers, a middle belt with little contrasting edges, slightly curved downwards, darker in older specimens, passes to the middle rays of the caudal fin, without black spot between the anus and anal fin, wide mouth. It is possible that this species has already entered the market under a different name.

C. oblongus is often a misused name in trade because this species has been described as bluish fish with yellow fins and has clearly never been exported because where it comes from is the streams of the active Salak Volcano (Gunung Salak) in western Java, Indonesia collecting ornamental fish is not practiced.

Other similar species

Other similar species with a transverse stripe may be available from time to time, but they are easier to distinguish from the group described above. For example, in C. nigriloba , the dark band clearly appears to form a series of spots – when the fish mate with each other, under stress or when asleep, and the lower lobe of the caudal fin has a dark red pigmentation.

C. burmicanus shows a blue color at the base of the pectoral fins. To add even more confusion, a slightly similar species Garra cambodgiensis (sometimes incorrectly labeled G. taeniata ) is often marketed as a false SAE mower, but is easy to tell because its dark band ends at the base of the tail, its whiskers are tiny and the jaw is disc-shaped and sometimes turns bright red on the outer lips. The species Epalzeorhynchos kalopterus  is also sometimes marketed as Crossocheilus, but exhibits several distinguishing features, the most obvious of which are reddish-black, white-edged fins.

The Paracrossochilus species from Borneo are also similar, but they are almost unheard of in the aquarium hobby.


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