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Betta simorum TAN & NG, 1996


simorum: named for Thomas G. K. Sim and his wife Farah, proprietors of Sindo Aquarium Pte. Ltd. ‘for being such excellent hosts during our stays in Jambi’.


Order: Perciformes Family: Osphronemidae


This species has been collected from various localities in the province of Jambi, Sumatra, the adjacent province of Riau, and the Kapuas River system in Kalimantan Barat (West Kalimantan) province, Borneo.

The type specimens were collected from ‘Swamp in Rantau Panjang, Jambi Province, Sumatra, Indonesia’, not to be confused with the town of the same name on the Thai-Malay border, whilst in Riau the species appears restricted to the Indragiri river basin.

Populations from different localities are often labelled as such by collectors and enthusiasts in order to maintain accuracy and preserve pure bloodlines, e.g., Rantau Panjang, Pematang Lumut (both in Jambi), Sungai Bengkwan (Riau), etc.


Inhabits heavily-vegetated forest peat swamps and associated black water streams.

These ancient biotopes are usually found in areas of rainforest, the dense canopy of branches above meaning very little light penetrates the water surface with riparianvegetation tending to grow thickly.

The water is typically stained darkly with humic acids and other chemicals released by decaying organic material.

The dissolved mineral content is generally negligible and the pH can be as low as 3.0 or 4.0.

The substrate is usually covered by fallen leaves, branches and submerged tree roots and at certain times of year the fish may be forced to survive within the moist leaf litter for several weeks as permanent water is not always available.

Maximum Standard Length

80 – 90 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions in excess of 80 ∗ 30 cm is recommended.


Can be maintained in a fully-decorated aquarium although many breeders prefer not to use a substrate for ease of maintenance.

Driftwood roots and branches can be used and placed such a way that a few shady spots are formed while clay plant pots or lengths of piping can also be included to provide further shelter.

The addition of dried leaf litter further emphasises the natural feel and as well as offering additional cover for the fish brings with it the growth of microbe colonies as decomposition occurs.

These can provide a valuable secondary food source for fry and the tannins and other chemicals released by the decaying leaves are also considered beneficial for fishes from blackwater environments.

There is no need to use natural peat, however, the collection of which is both unsustainable and environmentally-destructive.

Like others in the genus this species seems to do best under fairly dim lighting.

You could add aquatic plant species that can survive under such conditions such as Microsorum, Taxiphyllum or Cryptocoryne spp., and a few patches of floating vegetation would be useful as well.

This species requires acidic conditions with negligible carbonate hardness and very low general hardness so a reverse osmosis unit or other method of obtaining soft water may need to be employed, and this can be further acidified using phosphoric acid or similar if necessary.

As it naturally inhabits sluggish waters filtration should not be too strong, with an air-powered sponge filter set to turn over gently adequate.

Keep the tank well-covered and do not fill it to the top as like all Betta spp. it requires occasional access to the layer of humid air that will form above the water surface, and is an excellent jumper.

Water Conditions

Temperature25 – 30 °C

pH3.0 – 6.0

Hardness18 – 90 ppm


A study conducted in 1994 (in which the species was considered to be B. bellica) revealed a preference for odonate (dragon and damselfly) nymphs, although it probably predates on other small invertebrates as well.

Like B. bellica it’s a prodigious jumper and has been observed to leap from the water to catch prey from overhanging leaves or branches.

In captivity it will normally accept dried foods once they’re recognised as edible, but should be offered small live or frozen foods such as DaphniaArtemia or bloodworm regularly to ensure development of optimal colour and condition.

Take care not to overfeed as Betta spp. seem particularly prone to obesity.

Behaviour and CompatibilityTop ↑

Not recommended for the standard community set-up for reasons already touched upon.

It’s care requirements and disposition mean it is best kept alone or with very peaceful species since much bigger or more vigorous fishes are likely to intimidate it.

Some small cyprinids are suitable and it could even be maintained alongside other anabantoids given sufficient space.

Mixed reports exist as to whether it can be maintained in multiple pairs or harem-type groups comprising a single male alongside several females.

Some report that although some chasing and squabbling over territory occurs actual physical damage is rare, while others recommend keeping it in single pairs having observed sustained aggression towards conspecifics from the dominant individuals in a group.

Sexual Dimorphism

Mature males are more intensely-coloured and develop slightly more extended fins than females.


Bubble-nester. It’s particularly important to provide plenty of cover for the female, and  empty camera film canisters or lengths of plastic tubing are often used to offer potential nesting sites.

Floating plants may be incorporated into the nest if present.

The tank should have the tightest-fitting cover you can find (some breeders use clingfilm instead, to ensure no gaps) because the fry need access to a layer of warm, humid air without which development of the labyrinth organ can be impaired.

The pair need not be separated prior to spawning.

The male may construct the nest in a tube or canister, under a broad plant leaf or among fine-leaved surface vegetation, and will not usually tolerate the female in the vicinity until it’s complete.

Just prior to spawning the body colour of the female pales and dark bars appear on the flanks, with the act itself normally occurring below the nest in an ’embrace’ typical of anabantoids, with the male wrapping himself around the female.

At the point of climax milt and 5 – 20 eggs are released which the female proceeds to catch between pelvic fins and body.

The male then transfers them to his nest while the female recovers any that fell.

This cycle is then repeated until the female is spent of eggs, a process that can take some time.

Post-spawning the female is best removed as the male assumes sole responsibility for guarding and tending the nest, and may attack his former mate.

The eggs hatch in 24-48 hours, remaining in the nest for a further 3-4 days until the yolk sac is fully-absorbed, while the male continues to collect and return any that fall.

Once the fry begin to swim freely the male can also be removed as he may begin to eat them.

The fry are large enough to accept motile foods such as microworm and Artemia nauplii immediately, though it should be noted that there exist reports of young Betta developing health issues if fed excessive amounts of the latter.

Offer small amounts of different foods 2 -3 times per day for optimal growth rate, and don’t change too much water at once, with regular, small changes preferable to intermittent larger ones.

NotesTop ↑

This species is included in the B. bellica group of closely-related species within the genus, an assemblage of which members share the following set of characters: long and slender body with dorsal and ventral margins almost parallel; body depth 23-28 % SL; 30-33 anal-fin rays; 11-13 dorsal-fin rays; 32-34 total vertebrae; body dark brown in colour with iridescent green markings on each individual scale.

It can be distinguished from B. bellica, currently the only other member of the group, by the following characters: head slanted; dorsal surface of head noticeably concave behind eye; pelvic-fin tip extending to 14th anal-fin rays; pelvic-fin length 31.3-48.3 % SL; 33.5-35 lateral scales (mode 34); adpressed pelvic-fin reaching beyond anal-fin origin; distance between pelvic and anal-fin origins 8.5-13.1 % SL, mean 9.9.

The genus Betta is the most speciose within the family Osphronemidae with almost 70 recognised members and looks set to grow further with new ones continuing to be described on a regular basis since the turn of the century.

Member species have successfully adapted to inhabit a variety of ecological niches from stagnant ditches to flowing hill streams including some extreme environments such as highly acidic peat swamp forests.

The referral of members to a number of groups containing closely-related species is now generally accepted but largely based on morphological/behavioural characters.

Molecular phylogenetic work may therefore prove useful in more precisely determining relationships between these fishes.

A full list of the species groups as currently recognised can be found here.

Like others in the suborder Anabantoidei this species possesses an accessory breathing organ known as the labyrinth.

So-called due to its maze-like structure this organ allows the fish to breathe atmospheric air to a certain extent.

Comprising paired suprabranchial organs formed via expansion of the epibranchial (upper) section of the first gill arch and housed in a chamber above the gills, it contains many highly-vascularised, folded flaps of skin which function as a large respiratory surface.

Its structure varies in complexity between species, tending to be better-developed in those inhabiting harsher environments.


  1. Tan, H. H. and P. K. L. Ng, 1996 - Raffles Bulletin of Zoology 44(1): 143-155
    Redescription of Betta bellica Sauvage, 1884 (Teleostei: Belontiidae), with description of a new allied species from Sumatra.
  2. Schindler, I. and J. Schmidt, 2006 - Zeitschrift für Fischkunde 8(1/2): 47-69
    Review of the mouthbrooding Betta (Teleostei, Osphronemidae) from Thailand, with descriptions of two new species.
  3. Tan, H. H. and P. K. L. Ng, 2005 - Raffles Bulletin of Zoology Supplement (13): 115-138
    The labyrinth fishes (Teleostei: Anabantoidei, Channoidei) of Sumatra, Indonesia.
  4. Tan, H. H. and P. K. L. Ng, 2005 - Raffles Bulletin of Zoology Supplement (13): 43-99
    The fighting fishes (Teleostei: Osphronemidae: Genus Betta) of Singapore, Malaysia and Brunei.

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