Betta falx

Osphronemidae. Subfamily: Macropodusinae

Endemic to the Indonesian island of Sumatra. Most collections have occured in the central province of Jambi although it has also been recorded in the more northerly region of Utara. Populations from the different localities are often labelled as such by collectors/enthusiasts in order to maintain accuracy and preserve pure bloodlines i.e. Jambi or Sumatra Utara.

Typically inhabits forest swamp streams and pools. These are usually shaded from the sun, the dense canopy of branches above meaning very little light penetrates the water surface. Marginal vegetation also tends to grow thickly. The water itself is typically stained with humic acids and other chemicals released by decaying organic material. The dissolved mineral content is negligible, the pH quite low and the substrate composed mainly of fallen leaves, branches and submerged tree roots.

Around 2"/5cm.

An 18" x 12" x 12"/45cm x 30cm x 30cm/42.5 litre tank could easily house a pair of these. While some breeders maintain it in smaller tanks we prefer to see the fish in more spacious surroundings. If you want to keep a group correspondingly larger housing will be required.

This species can be maintained quite successfully in a well-planted, softwater tank but to see it at its best a biotope-style set-up is recommended. 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. Clay plant pots or lengths of piping can also be included to provide further shelter.

The addition of dried leaf litter (beech, oak or Ketapang almond leaves are all suitable; we like to use a mixture of all three) can further emphasise the natural feel, and as well as offering even more cover for the fish brings with it the growth of microbe colonies as decomposition occurs. These tiny creatures can provide a valuable secondary food source for fry, whilst the tannins and other chemicals released by the decaying leaves are thought to be beneficial for blackwater fish species such as this. Leaves can be left in the tank to break down fully or removed and replaced every few weeks.

Allow the wood and leaves to stain the water. A small net bag filled with aquarium-safe peat can also be added to the filter or hung over the edge of the tank to aid in the simulation of black water conditions. If you're like us, you'll just get hold of some genuine peat fibre and simply drop a few handfuls into the tank. This will become completely saturated 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 using either peat or leaves in an aquarium.

This species seems to do best under fairly dim lighting. You could add Asian plant species that can survive under such conditions, such as Microsorum pteropus, Taxiphyllum barbieri or perhaps some potted Cryptocorynes. A few patches of floating vegetation would be really useful to diffuse the light entering the tank too. As the species 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 the lowest flow setting. Keep the tank well-covered and do not fill it to the top as like all Anabantoids it requires access to a layer of humid air above the water surface. It is also an excellent jumper.

71.5 - 81°F/22 - 27°C

Not as fussy as some congeners. The pH in its natural waters has been recorded over the range 4.7 - 6.8 so provided conditions are on the acidic side of neutral no problems should arise.

Use soft water 0 - 5°H.

In nature it probably eats small insects and other invertebrates, but captive fish will normally accept dried foods once they are recognised as such. Like all fish it does best when offered a varied diet. In this case regular meals of live or frozen foods such as Daphnia, Artemia or bloodworm should ensure the development of the best colours and condition. Take care not to overfeed as Betta species seem particularly prone to obesity. Some experts have also warned of health problems developing when they're fed excessive quantities of Artemia, especially in young fish.

Not a recommended choice 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, small species. When kept alongside bigger or more vigorous tankmates it can be outcompeted for food and may become shy and withdrawn. Potential options include dwarf Corydoras, Otocinclus, and small cyprinids such as Trigonostigma or Boraras. Also note that the presence of any other fish in the tank can be a distracting influence should a pair decide to spawn.

Provided the tank contains plenty of hiding places and broken lines of sight there's no reason why a group of these cannot be maintained together. Although a little squabbling is inevitable (especially between males) it is generally quite a peaceful species.

As it's a paternal mouthbrooder the head of the male is noticeably larger than that of the female. Males are also the more colourful sex when mature, with bands of iridescent green/blue and dark pigmentation in the unpaired fins and some similar iridescence around the opercles (gill plates). Females do have bands in the fins but these are much thinner and fainter than in males.

By all accounts this species isn't too difficult to breed if the fish are provided with the correct water conditions and diet. You'll need to organise a separate tank for the purpose unless they are already being maintained alone, setting this up as suggested above. The tank should have the tightest-fitting cover you can find (some breeders use clingfilm 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.

A single pair or group of fish can be used, and feeding a varied diet containing plenty of live and frozen foods should bring them into spawning condition. It is the female that plays the more active role in both initiating courtship and defending the area against intruders. Eggs and sperm are released during a typical Anabantoid embrace in which the male wraps his body around that of the female. Several "practice" embraces may be observed before any eggs are released, in some cases several days before a genuine spawning event is seen.

Eggs are laid in small batches and are picked up in the mouth of the female before being spat out into the water for the male to catch. This process can take some time, sometimes with the pair even continuing to embrace before the female has got rid of all the eggs in her mouth. They are always collected again if the male misses them though.

Post-spawning the female continues to be the more dominant fish and some reports recommend removing her after a few days in case she wants to spawn again, disturbing the male before he has finished incubating. This normally takes 9 -12 days days at which point the male will begin to release fully-formed fry from his mouth. Apparently the parents will not harm these and some breeders have reported them to develop at a faster rate when left with the parents. However any other fish present (including conspecifics) do pose a threat to the young so in this scenario it's recommended to transfer fry or adults to a separate tank.

The fry are big enough to accept motile foods such as microworm and/or Artemia nauplii (see above notes on the feeding of Artemia to young Betta) immediately. Feed them small amounts of different foods 2 -3 times per day for the best rate of growth. Small (5 - 10% of tank volume) daily water changes can also be introduced to prevent organic wastes accumulating.

Betta falx was described by Tan and Kottelat in 1998 and is included in the Betta picta  complex of closely-related species, an assemblage which also includes B. pallida, B. simplex , B. taeniata  and of course B. picta .

In their 1995 review of the Anabantoids of Sumatra Tan and Ng noted the following: "Betta falx is closely related to B. picta  from Java. It differs from B. picta  in the following characters: lower dorsal fin ray count (mode 8 vs. 9); lower lateral scale count (mode 27 vs. 28); dorsal fin origin above 11-12th lateral scale (vs. 12-14th); anal fin origin below modal 6th lateral scale (vs. 7th); lower predorsal scale count (mode 19 vs. 20); slightly greater anal-fin base length (46.5-50.3% SL vs. 42.6-48.4); in life - males with distal margins of anal and caudal fins reddish (vs. bluish); iridescent greenish-blue opercle scales (vs. yellow-gold); preserved material - male with distinct dorsal transverse bars (vs. faint); male with distinct dark anal distal margin wide (vs. narrow); male without elongated median caudal fin rays (vs. presence); female with distinct caudal transverse bars (vs. very faint or absent); dorsal head view narrow (vs. broad); thick preorbital black stripe (vs. narrow); and the distance between posterior part of anal fin to lower part of caudal narrow (vs. wide)." In addition some experts state that the two can be distinguished by the presence of spots in the anal fin of falx that are not present in picta.

All species in the suborder Anabantoidei possess 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):43-99. 2005
   The fighting fishes (Teleostei: Osphronemidae: Genus Betta) of Singapore, Malaysia and Brunei.
2. 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.
3. www.fishbase.org
4. www.petfrd.com
5. www.ibcbettas.org