Arcadia Aquatics
  • Species: Microctenopoma ansorgeii

  • Species: Betta splendens - male

  • Species: Betta pugnax

  • Species: Colisa fasciata

  • Species: Colisa lalia 'blue neon'

  • Species: Ctenopoma acutirostre

  • Species: Ctenops nobilis

  • Species: Helostoma temminckii

  • Species: Osphronemus exodon

  • Species: Osphronemus goramy

  • Species: Parosphromenus deissneri

  • Species: Sphaerichthys osphromenoides

  • Species: Trichogaster chuna

  • Species: Trichogaster leeri

  • Species: Trichogaster pectoral

  • Species: Trichogaster trichopterus

  • Species: Trichopsis vittata

  • Species: Anabas testudineus testudineus

Unusual labyrinth fish

28 January 2017


Gouramis and bettas belong to a group of fishes known as labyrinth fish, characterised by a structure known as a labyrinth organ above the gills. This organ is used for breathing air, being richly supplied with blood vessels. Periodically the fish will gulp air, replenishing the air inside the labyrinth organ, and at the same time expels spent air through the gills. In the wild labyrinth fish are most common in slow moving or still waters, where their ability to breathe air gives them an advantage over other fish, particularly during the dry season where such waters can become stagnant. Most labyrinth fish are indifferent to water chemistry provided extremes are avoided, though these are a few exceptions (as will be noted in due course).

Labyrinth fish are perciform fish, and in outward appearance many species resemble other perciforms such as cichlids. In terms of basic care, many species are in fact very cichlid-like, being territorial but amenable to aquarium life and quick to learn to recognise their owner. They also exhibit a number of cichlid-like behaviours, including nest building, egg-guarding, and even mouthbrooding. Most labyrinth fish are robust and easy to keep, and on the whole can be expected to do well in most aquaria. Several species breed readily in home aquaria, though rearing the young tends to be more difficult than it is with cichlids because the fry are generally smaller. A peculiarity of many species is that they are bubble-nest builders, with the male placing the eggs in the nest and protecting them until the fry are free swimming. Other species are simple egg scatterers, while a few are mouthbrooders.

Labyrinth fish are divided into a four families, the Anabantidae, Belontiidae, Helostomatidae, and Osphronemidae. The Belontiidae is the family of prime importance to the aquarist, though species from all four families are traded periodically. The labyrinth fish group itself is referred to by scientists as the suborder Anabantoidei, from which comes the shorthand name for the group often used by aquarists: anabantoids.


The Anabantidae

Known colloquially as "climbing perches" this family includes three genera from Africa and one from Asia. The Asian genus is Anabas, of which Anabas testudineus is the one most likely to be seen. This species is famous for its ability to move overland, it is also able to survive the dry season by resting in a mud burrow in a manner similar to that of lungfish. Anabas testudineus has never really been a popular aquarium fish, and imports are rare. For one thing, it isn't very colourful, though it is certainly a neat, nicely proportioned animal. It is also rather unpredictable in terms of behaviour, sometimes shy and nervous, but at other time an outright bully. In fact, like a lot of oddball labyrinth fish, it is best kept with robust but non-aggressive and non-territorial tankmates such as plecs, large barbs and characins, spiny eels, and so on. Cichlids seem to bring out the worst in this fish (as well as labyrinth fish generally). For whatever reason, climbing perch seem not to be able to stand their ground against territorial cichlids of similar size. In aquaria, Anabas testudineus reaches 15-20 cm in length.

Among the African climbing perches, it is species of Ctenopoma and Microctenopoma that are most frequently encountered. Note that the name Microctenopoma has nothing to do with overall body size, and there are small species of Ctenopoma and large species of Microctenopoma. Of these African climbing perches, Ctenopoma acutirostre is by far the most commonly traded. Although predatory, this is an attractive and gentle fish that works well in quiet community tanks containing species of appropriate size. It is basically light brown with dark brown spots, and consequently known as the leopard bush fish by hobbyists. Although wild fish reach up to 20 cm in length, aquarium specimens are usually a bit smaller. Newly imported specimens are shy and almost nocturnal, but in a roomy aquarium with plenty of shade they will become more outgoing. In cramped aquaria or tanks without shade they will remain shy. Their preferred food in both the wild and the aquarium is insect larvae, particularly mosquito larvae and bloodworms. They will also eat small fishes up to female guppy size, but mix well with Congo tetras, dwarf Synodontis, peaceful bichirs, etc.

Microctenopoma ansorgii is very beautiful little climbing perch often referred to as the ornate ctenopoma. Getting to about 8 cm at most, these species is shy, very gentle, and in some ways quite demanding. It will not accept dried foods willingly, and prefers small live foods such as daphnia and bloodworms. Frozen substitutes are accepted after a period of acclimation. Being a slow feeder, it cannot easily be combined with other fish, though small, peaceful midwater and surface dwelling species might be an option, for example rabsoras and hatchetfish. In many ways it is very like the chameleon perch Badis badis, right down to its ability to change colours. Females and quiescent males are greenish with pale red and blue vertical bands that cross the body and fins. In breeding condition, males become much more intensely coloured, and must count as among the most attractive freshwater fish.

Microctenopoma fasciolatum is another small species and though not quite so attractive as Microctenopoma ansorgii, it is certainly a worthwhile species that makes a nice addition to the community tank. It is blue-grey to brownish in colour, with the male having brighter colours and more strongly defined vertical banding. In breeding condition, the males turn steel-blue and are quite striking little fish. Unlike the majority of climbing perches, this species is peaceful and quite readily accepts flake food


The Helostomatidae

There is only a single species in this family, the kissing gourami Helostoma temminckii. This fish used to be quite commonly traded, but it is now rather an unusual sight. Kissing gouramis can be found in two varieties, the normal greenish variety and a bright pink form. Its absence from the hobby can be largely put down to its adult size (around 15-20 cm being normal in aquaria) and its tendency to damage delicate plants while removing algae. As well as algae, in the wild this fish eats plankton, though in captivity a good quality algae-enriched flake food seems to make a good substitute. Like many plankton-feeders, requires several offerings of food per day; juveniles, in particular, are easily starved. It is fairly peaceful with other robust but non-aggressive species, and healthy specimens are active and attractive fish. It makes an excellent companion for things like plecs and other large catfish. Tends to get bothered by large, territorial cichlids though. Kissing gouramis are of course famous for "kissing". This behaviour seems to have multiple purposes. When kissing objects, these fish are actually removing algae, but when they kiss one another they may be fighting or testing one another prior to spawning.

The Osphronemidae

This family contains a single genus, Osphronemus, containing four species known as giant gouramis. On the plus side, these are exceptionally hardy, long-lived fish with lots of character, and in the right tank make excellent pets. They are territorial among their own kind by harmless towards other fish of similar size. However, on the downside, these fish are very large, and while undeniably cute and attractive when small, by the time they reach their adult size of 50 cm or more they are rather plain, even ugly. Nonetheless, they do get traded periodically, and adults make superb additions to tanks containing things like giant catfish and characins such as pacu. Giant gouramis are friendly and easily tamed, and quickly learn to be hand fed. Wild giant gouramis are omnivores, but plant material is particularly important to good health, so as well as standard flakes and pellets, provide algae pellets, pieces of cooked vegetables, soft fruit, and even things like cooked rice. Meaty treats like earthworms are also enjoyed. Osphronemus goramy (to 70 cm) is the usual species offered for sale, but two other species turn up less frequently. Osphronemus exodon (to 60 cm) is known by two common names, elephant-ear gourami and vampire gourami. The first name comes from the dark patch on the gill covers, supposedly reminiscent of the ears of an elephant; the second name refers to a unique feature of this species, the large teeth that jut out of the mouth. Osphronemus laticlavius (to 50 cm) is the red-tail or red-fin giant gourami that, as its common name suggests, is distinguished by the red edges to its unpaired fins.

The Belontiidae

As mentioned earlier, the Belontiidae is the most important family as far as the aquarist is concerned, with numerous species regularly traded. Of these, the Siamese fighting fish, dwarf gourami, three-spot gourami, lace gourami, and moonlight gourami can all be considered "common" species, but while they may be easy to buy, they don't all make great community fish. The Siamese fighting fish Betta splendens has been selectively bred over decades to produce a brightly coloured, long-finned fish that may look beautiful but fares poorly in most community tanks. The dwarf gourami Colisa lalia is another problematical species. Wild fish may be sturdy creatures, but the tank-bred stock commercially available from Singapore in particular has been plagued with a virus known as DGIV (dwarf gourami iridovirus). Infected fish stop eating and moving about, and eventually the internal organs swell and the fish dies. There is no known cure, and DGIV appears to be highly contagious, so that once one dwarf gourami in a tank gets sick, they all do. The three-spot gourami Trichogaster trichopterus comes in two main colour forms, blue and yellow, and it is quite common to see both sold as blue gouramis and yellow gouramis respectively. Names aside, these fish are very robust and easy to care for, but the males are notoriously waspish, and many an aquarist has had a peaceful community tank turned upside down by a territorial three spot gourami. Lace gouramis and moonlight gouramis, Trichogaster leerii and Trichogaster microlepis respectively, are perhaps the best of the common gouramis for the community tank, being invariably peaceful and accommodating in nature, but they are a little less hardy than the three-spot gourami, and aren't so vividly coloured.

Having looked at the common species, let us turn to the less frequently seen species. To begin with there are multiple species of Betta that are imported on a fairly regular basis. Most are more or less peaceful towards inoffensive fishes of appropriate size, though the larger species are distinctly predatory. Betta pugnax (to 10 cm) is a typical example of the mouthbrooding bettas, and is generally an easy fish to care for. It will eat very small species such as neons, but is otherwise harmless and can be kept in community tanks. Males are territorial, but in large, well planted aquaria may coexist without problems. Unlike Siamese fighting fishes, Betta pugnax lives in streams rather than ditches, and as such appreciates good water quality and a bit of water movement.

The thick-lipped gourami Colisa labiosus (to 9 cm) is an especially nice labyrinth fish, and makes an excellent alternative to the troublesome dwarf gourami. Similar in shape and colour, though with a bit more red and a little less blue, this is one species definitely worth looking out for. In terms of behaviour is very mild, though breeding males can be a little short tempered (but that is true for the dwarf gourami, too). The banded gourami Colisa fasciata (to 12 cm) is another dwarf gourami look-alike, and also makes an excellent community aquarium resident.

The frail gourami Ctenops nobilis (to 10 cm) is a strange, rather difficult species that does not seem to adapt well to the home aquarium. Best results seem to occur when the fish is kept in neutral, slightly soft water and at moderately cool water (20-24 degrees C). Water quality needs to be excellent, otherwise they are prone to a variety of sicknesses. While an interesting species for the advanced aquarist, these fish are otherwise best avoided.

Malpulutta kretseri (to 4 cm) is a distinctively marked species from Sri Lanka that is quite rare in the wild and only traded infrequently. In shape it resembles a small betta, but with a checkerboard pattern of light and dark spots. It is peaceful and fairly easy to care for, but appreciates good water quality and plenty of plants to hide among.

Another small species is Parosphromenus deissneri (to 3 cm), the liquorice gourami. Though beautiful and much sought after by discerning aquarists, this isn't an easy species to keep. Soft and acidic water is essential and water quality must be excellent. When stressed these fish lose their colours, but once settled into a quiet, thickly vegetated aquarium they become very attractive, with chocolate brown stripes along the body and red and blue markings on the fins. There are a number of other Parosphromenus species traded periodically, and these need to be kept in much the same way. The chocolate gourami Sphaerichthys osphromenoides (to 6 cm) is not dissimilar in needs to Parosphromenus, and is another interesting species for the ambitious aquarist. Like some of the bettas, but unlike most of the gouramis, it is a mouthbrooder.

A couple of additional species of Trichogaster are imported from time to time. Trichogaster chuna (to 7 cm) is known as the honey gourami and though a little more delicate than the common gourami species, it is far from difficult to keep if provided with clean water and a quiet aquarium. Plants, especially floating plants, are appreciate. Females are pinkish grey while males are golden brown with a beautiful blue fringe to the dorsal fin. In breeding condition, the ventral surfaces of the male's head and body turn black and the overall tone of his body colour becomes much more intense. There are some artificial varieties of this species, including an all-gold form. The snakeskin gourami Trichogaster pectoralis (to 25 cm) is a very rarely seen species, not because it is a delicate or aggressive fish, but because it lacks bright colours and gets rather large. Looking a bit like a very large, brownish three-spot gourami, it is basically hardy and peaceful, and could be put to good use in a community tank containing catfish, large barbs, etc. Its primary value is as a food fish rather than an aquarium fish.

The genus Trichopsis contains three species known for their ability to produce distinctly audible noises, for which reason they are often called the croaking gouramis. Trichopsis vittata is the largest at up to 7 cm, and Trichopsis pumila the smallest at a mere 4 cm, with Trichopsis schalleri in between them at about 5 cm in length. All are peaceful, essentially hardy fish well suited to community aquaria alongside fishes of appropriate size. They live in sluggish, thickly vegetated waters where they feed on plankton and insect larvae. Trichopsis vittata is perhaps the most widely sold, and has a silvery blue body bearing a delicate pattern of shiny spots and a dark band running along the midline of the fish from snout to tail.

Further reading

For the aquarist interested in labyrinth fish, the Aqualog "All Labyrinths" book is essential reading. click here.


Summary

The labyrinth fishes offer plenty of interest for both advanced aquarists and beginners, and the majority of species are suitable for inclusion in community tanks provided their requirements for water quality and water chemistry are met. Few species are so aggressive or so delicate that they cannot be combined with tankmates, and many do well in hard, alkaline water. Enterprising aquarium shops are regularly bringing in new species, and a lot of old favourites like the kissing gourami can still be found without too much bother. Though perhaps overshadowed by the cichlids in many ways, labyrinth fish are a fascinating group well worth getting to know better.

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