Sphaerichthys osphromenoides - Chocolate Gourami

Osphronemidae. Subfamily: Luciocephalinae

By far the most widely distributed species in the genus, it's native to parts of Malaysia as well as the islands of Borneo and Sumatra.

Inhabits peat swamps and associated black water streams. These ancient biotopes are found in forested areas and contain water that is typically stained dark brown by humic acids and other chemicals released from decaying organic material. This results in a negligible dissolved mineral content and the pH can drop as low as 3.0 or 4.0. The dense rainforest canopy above means that very little light penetrates the water surface and the substrate is normally littered with fallen tree branches and rotting leaves.

Fully grown at 2.4"/6cm.

Can be quite tricky to acclimatise to aquarium life and above all else requires stable water conditions in order to thrive. As smaller tanks are more susceptible to rapid fluctuations in water chemistry we think that a something around 30" x 12" x 12"/75cm x 30cm x 30cm/70.8 litres in size should be the smallest considered to house a group of these. Using a slightly larger tank is also preferable as the species seems to be territorial to a certain degree or at the very least groups exist in defined hierarchies. It also exhibits some interesting behaviour which is thought to be involved in the organisation of these social structures (see section below).

This species isn't really recommended for most tanks due to its exceptionally shy nature and particular water requirements. It can be maintained quite successfully in a well-planted, softwater tank but to see it at its best a natural-style set-up is preferable. Despite not being particularly representative of its natural waters a soft, sandy substrate is probably the best choice here not least because it would be impossible to accurately simulate a peat swamp habitat in an aquarium! Add a few driftwood roots and branches, placing these in such a way that a few shady spots are formed. If you can't find driftwood of the desired shape common beech or oak is safe to use if thoroughly dried and stripped of bark. A few handfuls of dried leaves (beech, oak or Ketapang almond leaves are suitable and a mixture of all three looks really good) would complete the wild feel.

Allow the wood and leaves to stain the water brown. A small net bag filled with aquarium-safe peat can be added to the filter to aid in the simulation of black water conditions. Alternatively just get hold of some real peat fibre and drop a few handfuls into the tank. This will become completely soaked with water after a few days and sink to the bottom. Provided a good routine of water maintenance is practiced no adverse effects should occur.

In this kind of set-up fairly dim lighting works better. You could add Asian plant species that can survive under such conditions such as Java fern (Microsorum pteropus), Java moss (Taxiphyllum barbieri) or Cryptocorynes. A few patches of floating vegetation would be really useful to diffuse the light and provide extra cover too.

Ideally leave the tank to mature for a good few weeks before adding the fish as this species has proved to be particularly sensitive to the swings in water chemistry that tend to occur in immature set-ups. As it hails from sluggish waters filtration should not be too strong. An air-powered sponge filter set to turn over slowly is adequate or if using a power filter adjust it to a low flow setting. Keep the tank well-covered or lower the water level a few inches as like other Anabantoids it benefits if there is a layer of humid air above the surface. As the species is so sensitive to fluctuations in water parameters small (say 10% of tank volume) regular water changes are essential to keep it in good health. Changing larger amounts than this could prove detrimental to the fish.

As is the way in fishkeeping we know of a handful of cases in which Sphaerichthys osphromenoides has been maintained in "standard" community tanks with no apparent ill effects, but this is not something we advocate. It should be noted that that these cases are the exception to the rule with this species, perhaps even indicating captive-bred fish.

Prefers warm water in the range 79 - 88°F/26-31°C.

4.0 - 6.0. It's natural waters are characteristically acidic and it will struggle in alkaline conditions.

Use very soft water 0 - 5°H.

Feeds on a variety of insects, zooplankton and occasionally the fry of other fish in nature. In our experience the species is not nearly as fussy to feed as is often reported although it does seem to fare best when offered regular meals of small live foods such as Daphnia or Artemia. These are especially useful when acclimatising newly-imported specimens or conditioning the fish to breed. Frozen alternatives are perfectly acceptable in most cases and even dried foods are often taken without fuss. If your Sphaerichthys osphromenoides are refusing to eat the problem most likely lies in the water conditions although wild caught fish have been known to harbour internal parasites or other bugs on occasion.

Not a fantastic choice for the community for reasons already touched upon. It's care requirements and retiring disposition mean it is best kept alone or with other small, quiet species that enjoy similar conditions. If you do decide to keep chocolate gouramis alongside other types of fish try to build your choice around them rather than the other way around. A tank set up to house this species should be just that. Thus larger or more aggressive species are out as are other anabantoids, cichlids or very vigorous feeders such as many barbs.

Any of the popular Trigonostigma species make decent tankmates as do some other small cyprinids such as Boraras and some Rasboras. For the lower regions of the tank many freshwater shrimps of the genus Neocaridina are ideal to add a bit of extra interest. The dwarf chain loach Yasuhikotakia sidthimunki  is often quoted as being suitable although in smaller tanks we suspect these might bother the gouramis with their perpetual movement and lively feeding habits. If geography is not an issue a shoal of one of the dwarf Corydoras or Otocinclus species could also work well.

Despite being such a poor competitor with other species this species can display a surprising amount of aggression towards conspecifics at times. Groups develop noticeable hierarchies and you'll often see dominant individuals chasing away their rivals at feeding time or when occupying their favourite spot. Several hobbyists have also observed an intriguing behaviour in which an individual will lie on its side and allow another member of the group to mouth its body and fins. No damage has ever been noticed during these displays and neither do they seem to form part of any spawning ritual. Some have suggested it may be a method of establishing dominance between the fish but at present this can only be considered speculation. It is definitely a social animal though and should be maintained in numbers so that natural patterns of behaviour can develop.

Males possess a white edge to the the dorsal and anal fins and a more intensley coloured, sometimes scarlet-infused body. Females tend to exhibit a more rounded head profile (probably an adaptation that allows the mouthparts to become distended during broodcare) and have a dark spot on the caudal fin.

This species is supposed to be difficult to breed but if the fish are maintained in the correct conditions and fed a good diet it is certainly possible. Historically there has been some confusion surrounding its breeding strategy with some sources listing it erroneously as a bubblenester or paternal mouthbrooder. It is a maternal mouthbrooder with the female incubating the eggs in her mouth for up to two weeks before releasing the fully-formed fry. Success has been achieved using both groups or single pairs of fish and by removing the brooding fish to a separate tank or leaving the fry in with the adults to fend for themselves.

A tank set up as described above makes an ideal environment as it provides plenty of cover for the fry. If using a substrate of peat fibre and leaf litter (highly recommended) there should be a thriving colony of microrganisms present too which will provide an additional source of food for the young fish. The tank should have the tightest-fitting cover you can find (some breeders use clingfilm/shrinkwrap instead to ensure no gaps) as the fry need access to a layer of warm, humid air. Without this the development of the labyrinth organ can be impaired. The water in the tank should be warm, soft, acidic and aged. Suggested parameters are temperature 79 - 88°F/26-31°C, pH 5.0 - 6.0, gH <5°. The use of a peat substrate or filtering the water over peat is considered essential to success by most breeders but it has been done without.

Add a pair or group of adult fish to the tank, feed them on a high quality diet with plenty of small live and frozen foods and nature should take its course eventually. If you intend to rear a decent number of fry then you'll also need to set up a second tank containing identical water to the first in order to separate brooding females. These are easily recognised by their distended mouthparts and characteristic "chewing" action. If the brooding fish are left in situ then some fry should still survive if the tank is well-furnished and properly matured.

During the brooding period the female will refuse food and will often be seen lurking in the quiet, shadier parts of the tank. She will keep the eggs/fry in her mouth for 7 - 12 days on average eventually spitting out (literally!) around 20 - 40 fully-formed fry. These will require several small meals per day and are big enough to handle motile foods such as microworm or Artemia nauplii immediately. Daily water changes of around 10% of tank volume should also be performed in order to maintain water quality and achieve a good rate of growth.

The genus Sphaerichthys currently comprises four species with Sphaerichthys osphromenoides being by far the best known to hobbyists. It is a somewhat confusing group as some species exhibit reversed sexual dimorphism (S. vaillanti, S. selatanensis) while S. osphronemoides apparently does not. Of the others only S. vaillanti has been seen in the trade with anything approaching regularity and then only in recent years. It is difficult to confuse with Sphaerichthys osphromenoides having a more pointed/elongate head profile and totally different patterning. S. acrostoma has a similar overall shape to S. vaillanti but the patterning on the body is much plainer. S. selatanensis most closely resembles Sphaerichthys osphromenoides (it was originally considered to be a subspecies) and is best identified by the presence of a pale longitudinal stripe extending from the top of the caudal peduncle to the opercle. All are best left to the more-experienced fishkeeper as they have rather specific requirements in one way or another.

Sphaerichthys are grouped within the Osphronemid subfamily Luciocephalinae along with Colisa, Trichogaster, Luciocephalus, Parasphaerichthys and Ctenops species. The latter trio share an egg structure with Sphaerichthys that is unique among teleosts; the distinguishing factor consisting of a series of spiralling ridges on the outer surface. This has given rise to the (as yet unproven) theory that the four genera form a monophyletic group ie. they share a common genetic ancestor. In Luciocephalus and Sphaerichthys the eggs are also distinctively pear-shaped suggesting that these two share even closer genetic roots.

Like others in the suborder Anabantoidei this species possesses an accessory breathing organ known as the labyrinth organ. So-called due to its maze-like structure this organ allows the fish to breathe atmospheric air to a certain extent. It is formed by a modification of the first gill arch and consists of many highly vascularised, folded flaps of skin. The structure of the organ varies in complexity between species tending to be more well-developed in those inhabiting particularly oxygen-deprived conditions.

Literature cited

1. Tan, H.H. and P.K.L. Ng. - Raffles Bull. Zool. Supplement (13):115-138. 2005
   The labyrinth fishes (Teleostei: Anabantoidei, Channoidei) of Sumatra, Indonesia.
2. www.fishbase.org
3. www.petfrd.com