Max. Length: 5cm
Min. Aquarium Size: 60 x 30cm (base dimensions)
Temperature: 23 – 30 °C
pH: Wild specimens will require a pH within the range of 4.0 – 6.5 in order to thrive, however, tank-raised individuals are normally more adaptable.
Hardness: 0 – 54 ppm for wild fish, up to 10° if captive-bred.
Chocolate Gouramis are a unique fish to the aquarium hobby. Unlike other labyrinth fish found in the hobby, Chocolate Gouramis are relatively rare. This gives them a special appeal for hobbyists like myself, who take pride in keeping fish that few other people keep. In Australia, this fish is becoming harder and harder to find, as the government has recently passed a law which states that certain fish species (Chocolate Gouramis included) have to be free from iridovirus for six months before they are imported.
Chocolate Gouramis (Sphaerichthys osphromenoides osphromenoides) are native to Peninsular Malaysia, Sumatra and Borneo. They typically inhabit peat swamps and associated black water streams. However, they can also be found clear water habitats, typically slow moving streams. The black water habitats contain water that is typically stained dark brown by tannins and humic substances, released by decaying organic matter. This results in a negligible dissolved mineral content and the pH can drop as low as 3.0 or 4.0. Waterways such as this are typically located in dense rainforest, where the rainforest canopy results in both, very little light penetrating the water’s surface and the substrate being littered with fallen tree branches and rotting leaves.
Clear water habitats have similar water chemistry to black water habitats but in most cases dense aquatic vegetation is present. Aquatic plants found in these areas often include the following genera; Cryptocoryne, Blyxa, Barclaya, Eleocharis, Utricularia, and Lymnophila.
Species found alongside S. osphromenoides, include; Trigonopoma pauciperforatum, Luciocephalus pulcher, Nandus nebulosus, Rasbora einthovenii, Boraras maculatus, Belontia hasselti, Betta waseri, B. tussyae, B. imbellis, and Kryptopterus macrocephalus.
Adult males exhibit a uniformly straight lower jaw line and an overall more pointed head shape than females. Females have a more rounded lower jaw, due to the presence of distensible skin that is expanded during mouth brooding. Males also possess relatively longer and more pointed unpaired fins and exhibit more intense colouration. However, the latter two points are not applicable in all cases, which may be due to geographic variance.
In the wild, the Chocolate Gourami is a micro-predator, feeding on small aquatic crustaceans, worms, insect larvae and other zooplankton. Although this fish can be a little picky in the aquarium, they may not accept dried or prepared foods initially, they will in most cases learn to take them over time. Daily meals of small live or frozen food, such as Artemia nauplii, blood worm, Daphnia, grindal worm, micro worm, etc., should be offered in order to keep these fish in optimum health. These foods will also encourage the development of colour and help condition them for breeding.
This species is unfussy in regards to décor, provided adequate cover and structure is available. A range of artificial décor can be used, including; ceramic flowerpots, plastic piping etc. However, a more natural arrangement will encourage more natural behaviour. A natural arrangement usually consists of a soft, sandy substrate with wood roots and branches to provide cover and hiding places. The addition of dried leaf litter (beech, oak or Ketapang almond leaves) further replicates the natural environment. The tannins and humic substances released by the decaying leaves aids in the simulation of a black water environment. The addition of leaf litter is also beneficial to fry of this species, as the fry are able to feed on the microbes which grow on the leaves as decomposition occurs. Leaves can be left in the tank to break down fully or removed and replaced every few weeks.
This species seems to do best under fairly dim lighting and plant species from genera such as Microsorum, Taxiphyllum, Cryptocoryne, and Anubias are recommended since they will grow under such conditions. A few patches of floating vegetation to diffuse the light even further may also prove effective.
As this fish naturally inhabits sluggish or still water environments, filtration or at least water flow, should not be very strong. Very large water changes should also be avoided. 10-15% weekly water changes are adequate, provided the tank is lightly-stocked.
Behaviour and Compatibility
Tank mates must be chosen with care because this species is slow-moving and will easily be intimidated or outcompeted for food by larger, more boisterous tank mates. Peaceful, pelagic cyprinids such as Danionella, Microdevario, Trigonostigma, or smaller Rasbora species make excellent choices as do some loaches such as Pangio or Kottelatlimia spp. This species should not be combined with S. selatanensis, as hybridisation is likely to occur.
Although not a schooling fish, Chocolate Gouramis are gregarious and require interaction with other members of the same species. No less than six individuals should be kept at one time. Any less causes aggression and infighting. When kept in groups, noticeable hierarchies develop. The dominant individuals will chase away their rivals at feeding time or when occupying their favourite spot.