Etymology

dimidiata: from the Latin dimidiata, meaning ‘halved, diminished’, in reference to the small size of this species.

Distribution

Type locality is ‘Kapuas basin, Sungai Seriang, 37 kilometers west of Putussibau, Indonesia’.

The Seriang is a tributary in the Kapuas River system, Kalimantan Barat (West Kalimantan) province, Borneo, Indonesia and the species appears to be endemic to the upper portion of the Kapuas drainage including the Danau Sentarum lakes region.

Habitat

Typically inhabits forest swamp streams and pools, some of which have been measured at just a few centimetres deep.

These are usually shaded from the sun, the dense canopy of branches above meaning very little light penetrates the water surface while riparian vegetation also tends to grow thickly.

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

The dissolved mineral content is negligible, pH quite low and substrate composed mainly of fallen leaves, branches and submerged tree roots.

At certain times of year the fish may be forced to survive within the moist leaf litter or in holes in the river-bed for several weeks as permanent water is not always available.

Maximum Standard Length

35 – 40 mm.

Aquarium Size

An  aquarium with base measurements of 45 ∗ 30 cm could house a pair or small group.

Maintenance

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

Temperature: 22 – 27 °C

pH: The pH in its natural waters has been recorded over the range 5.2 – 6.5.

Hardness: 18 – 90 ppm

Diet

Likely to prey on insects and other small invertebrates in nature.

Captive fish will normally accept dried products once they’re recognised as edible, but should be offered plenty of small live or frozen foods such as Daphnia, Artemia or bloodworm regularly to ensure development of optimum colour and condition.

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

Behaviour and Compatibility

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

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

Some small cyprinids and loaches that inhabit similar environments in nature are compatible, but proper research prior to purchase is essential.

It can be maintained in a pair or group and will display some interesting behavioural interactions under the latter circumstances.

Sexual Dimorphism

Males grow larger, possess a greater amount of iridescent scaling on the head, a broader head shape, and more extended fins than females.