Into the Peat Swamps of Borneo: The World of Betta hendra

Species Spotlight · Blackwater Habitats · Wild Bettas

Some fish look good under bright store LEDs. Others make you want to understand the place they came from. Betta hendra belongs firmly in the second group.

This small, green-flanked wild betta is known only from the Sabangau peat swamp forest of Central Kalimantan, Borneo, one of the most remarkable and threatened ecosystems on Earth. To keep it well, you first have to understand where it lives. After that, you won't look at a handful of leaf litter the same way again.

Betta hendra at home in our Sabangau-inspired tank. Photo: Blackwater Scapes.

The Place: Sabangau, Central Kalimantan

Picture a flooded forest stretching to the horizon. The canopy is so dense that sunlight reaches the water in scattered patches. The water is shallow, still, and the color of dark tea, stained by peat, leaves, and bark that have been breaking down for thousands of years.

The collection site of Betta hendra (dot), south of Palangka Raya in Central Kalimantan. Map: Schindler & Linke (2013), Vertebrate Zoology, CC BY 4.0; resized to fit.

This is the Sabangau (Sebangau) River basin, just south and west of Palangka Raya, the provincial capital. It is one of the largest remaining lowland peat swamp forests in Borneo, and Sebangau National Park holds the largest known population of Critically Endangered Bornean orangutans [6]. It is also the only known home of Betta hendra [2]. The type locality sits about 3 km southeast of Palangka Raya, toward Berengbengkel [1].

Water at the Type Locality

When the habitat was measured in May 2011, the readings showed just how extreme it is [1]:

The water is shaded by trees and bushes, and the fish were collected among aquatic and marsh plants [1]. By most aquarium standards it is an extreme environment. For Betta hendra, it is home.

Sabangau is extreme, but not unusual for Borneo's wild bettas. Across Kalimantan, they live in soft, tannin-rich water with a pH of 3.5–6.0, over soft, spongy mud and dense leaf litter, with little light reaching the water. Those conditions also leave little dissolved oxygen, which bettas cope with by breathing air at the surface [11].

A Peat Swamp, Not a River

Sabangau is an ombrogenous peat swamp: a rain-fed system sitting on meters of waterlogged peat. Almost no minerals wash in from rock or runoff. The acidity comes from the peat itself and the constant breakdown of plant matter.

That is a different engine from an Amazonian igapó, a blackwater river forest that floods seasonally with each rise of the river. Both run dark and acidic. Borneo's peat swamp is standing water shaped by peat; the igapó is shaped by a flood pulse.

The peatlands around Sebangau and Palangka Raya formed during the Holocene, after the last ice age. The scientists who described B. hendra suggest the species split from its relatives during this most recent geological epoch [1].

Knowing that difference is what separates a generic blackwater tank from a true biotope.

The Fish: A Green Gem of the Coccina Group

Betta hendra was described in 2013 by Ingo Schindler and Horst Linke [1]. It is named for Hendra Tommy of Kurnia Aquarium in Palangka Raya, who discovered the fish and first exported it [2]. It belongs to the Betta coccina group, a set of small wild bettas from acidic peat swamps.

What sets it apart:

• Size: wild-caught adults stay under 3 cm (1.2 in) standard length, but captive-raised fish can reach 4.5 cm (1.8 in) [1].
• Color: males carry iridescent greenish-blue metallic scales along the flanks under a dark brown back, two bright red-to-golden vertical bars on the gill cover, and reddish-brown fins speckled with greenish blue. Those bright green flanks set it apart from every other coccina-group species [1].
• Males vs. females: females look similar but have fewer iridescent scales and paler gill-cover bars [1].
• Fin rays: 10–12 dorsal-fin rays, which separates it from its geographic neighbor, Betta uberis [1].
• Breathing: like other bettas, it has a labyrinth organ that lets it gulp air at the surface, an adaptation to oxygen-poor swamp water [11].

The two red bars on the gill cover, one of the species' field marks. Photo: Blackwater Scapes.

Under white light, an adult male shows the greenish-blue flanks that identify the species. Photo: Schindler & Linke (2013), Vertebrate Zoology, CC BY 4.0; background extended to fit.

Unlike Betta splendens, it is a secretive, mostly peaceful fish. It spends its time threading through roots, leaf litter, and low vegetation.

At some sites it lives alongside Betta foerschi, a larger peat swamp betta that grows past 4 cm (1.6 in) [1]. Two larger Endangered peat swamp bettas, B. foerschi and B. strohi, are both recorded from the Sebangau drainage [11]. The describers also suggest B. hendra may be one of the earliest-branching members of the coccina group [1].

A Conservation Note

Betta hendra is listed as Critically Endangered on the IUCN Red List [4]. Its known range covers less than 10 km² (under 4 square miles) [5]. The main threat is the conversion of peat swamp forest to industrial forestry and monoculture plantations, and uncontrolled fire is a growing risk. Whether collection for the aquarium trade also harms wild populations is still uncertain [11].

The forest itself is shrinking fast. Over two decades, forest cover on Southeast Asia's peatlands fell from 77% to 36%, and researchers estimate that more than half of the fish species restricted to this habitat could go extinct within three to four decades (Miettinen et al. 2012 and Giam et al. 2012, as cited in [1]).

Fire makes it worse. Peat swamp forest has already been reduced by more than 60% in parts of Borneo, and fires, often set to clear land, spread fastest in El Niño drought years. Burning peat also releases toxic compounds into the water, changing its chemistry and stressing the fish that live there (Miettinen et al. 2011 and Field et al. 2009, as cited in [11]).

The 2026 fire season

That threat is not abstract. An exceptionally strong El Niño drought has left Central Kalimantan's peatlands dangerously dry this year. In early September 2026, fire crossed into Sebangau National Park for the first time this season, and a fire line more than 30 km long was burning along the park's northeastern edge [6]. Community firefighters pushed back the fire that entered the park, and no primary forest was lost there. A nearby reforestation site holding about 45,000 young saplings was destroyed [6].

If you'd like to help protect the forest this fish comes from, Borneo Nature Foundation's emergency firefighting appeal funds the community teams working in Sebangau.

Buy captive-bred fish whenever you can. Every fish raised in the hobby takes a little pressure off a wild population with nowhere left to retreat.

Recreating Sabangau: Water Chemistry First

The goal is not a clean tank. The goal is an honest one, and that starts with the water. Betta hendra is far less forgiving about chemistry than B. splendens.

Our Sabangau-inspired tank: tea-stained water, root tangles, a peat and leaf-litter floor, and a floating-plant canopy. Photo: Blackwater Scapes.

You don't need to hit pH 4.0 to succeed. The first documented captive breeding of this species was achieved at pH 6.35–6.40 and 28.0–28.6 °C [5]. Soft, mineral-poor water matters more than chasing the lowest possible number.

A few rules:

• Skip crushed coral, limestone, and other substrates that raise pH.
• Remove activated carbon from the filter; it strips out the tannins your tank depends on.
• Avoid untreated tap water unless your source is already very soft.

Go slowly

RO water has almost no buffering capacity, so a young tank can swing quickly. A large, sudden load of fresh leaves can drop pH sharply over a few days. Add botanicals in stages over several weeks, let biofilm and detritus build up, and keep the bioload light at first. Test often until readings hold steady.

The Botanical Foundation, Built for Borneo

In Sabangau, the water chemistry is made and maintained by the forest itself: leaves, roots, and wood breaking down into the peat. A habitat-true tank uses plants that actually belong to Southeast Asia's swamp forests, not just anything that tints the water.

Boil or soak denser roots for 24–48 hours before adding them so they sink and release their first flush of tannins. Add peat gradually; it can lower pH quickly in RO water.

Leaves, peat, and roots breaking down together on the floor of our tank. Photo: Blackwater Scapes.

If you only ever reach for catappa, you have a blackwater tank. When you build on swamp fern, Bornean leaves, and root tangles, you are getting closer to a Sabangau tank.

All five botanicals in this table come together in our Sabangau Peat Swamp Kit.

Tank Size and Layout

A 10–20 gallon (38–76 L) tank suits a pair or a small group. Betta hendra doesn't need open swimming space. It needs density: visual barriers, tight hiding spots, and the feeling of being surrounded by structure.

Floating plants dim the light and drop a curtain of roots, much like the canopy over a peat swamp. Photo: Blackwater Scapes.

• Lighting: low and warm. Floating plants dim the surface and recreate the canopy-filtered light of the forest floor.
• Cover: a deep leaf-litter layer, root tangles, and a few pieces of wood break up sight lines between males.
• Lid: keep the tank covered and leave an air gap above the water. Like all bettas, they breathe at the surface and can jump.
• Tank mates: males can be territorial with each other. If you add companions, choose small, calm fish that share a need for very soft, acidic water.

Peeking out from under a branch. Plenty of cover keeps these shy fish confident. Photo: Blackwater Scapes.

When in doubt, a species-only tank is both the most authentic and the most reliable choice.

Breeding: A Bubble-Nester Worth the Patience

Like most of the coccina group, Betta hendra builds bubble nests [1]. The male usually tucks the nest under a broad leaf, beneath wood, or in a sheltered corner, then guards it.

1. Condition first. Feed a rich, varied diet of live foods before pairing. In the first documented captive breeding, researchers fed live Moina (a small water flea) and mosquito larvae daily, and the fish were ready to breed after about 30 days [5]. Microworms, grindal worms, and small daphnia work well too.
2. Pair them. Give each pair a small tank with a couple of dried catappa leaves and a shelter. Males build bubble nests under dried leaves or in a corner. Some pairs spawned within two days, but timing varied widely, from 2 to 30 days after pairing and about 11 days on average [5].
3. The spawn. The pair embraces beneath the nest. The eggs sink, and both parents collect them and place them in the nest. Spawns in the study ranged from 19 to 92 eggs, about 59 on average [5].
4. Remove the female. Once spawning ends, the female often tries to eat the eggs, so move her to another tank right away [5].
5. Leave the male until the eggs hatch. With the male guarding the nest, every spawn hatched. Without him, fewer than half the eggs hatched and fungus spread on the untended eggs. After hatching, though, the male competes with the larvae for food, so remove him then [5].
6. Feed the fry. Larvae begin feeding about 4 days after hatching and show pigment by day 7. Fry fed newly hatched brine shrimp reached about 6 mm by 18 days [5]. Feed small amounts often, since overfeeding brine shrimp has been linked to health problems in young bettas [3].

Why This Fish Matters to the Botanical Hobby

Betta hendra is not a casual purchase. It asks for a style of fishkeeping where water chemistry, slow decomposition, and a maturing ecosystem matter more than routine pH corrections.

The people who keep it well understand that tannin-stained water is not dirty water, and that decomposing leaves are not waste. A Bornean peat swamp is dark, still, and full of life. Recreating even a small corner of one is a meaningful thing to do with a glass box and a handful of botanicals.

Hobbyists matter here too. Captive breeding of Borneo's wild bettas is still mostly in hobbyists' hands, and researchers are calling for hobbyists, scientists, and conservation groups to work together: keeping breeding records, maintaining genetically diverse lines, and sharing what works. Well-kept captive populations can serve as a genetic reserve if wild habitat collapses [11].

The Sabangau is shrinking. The fish in your tank may help the species endure outside its homeland. Keep the water dark, keep it soft, and keep a few leaves on the bottom.

Where Sunken Forests Come to Life.

Build Your Own Sabangau

Ready to bring a piece of Borneo home? Our Sabangau Peat Swamp Kit brings together all five botanicals from this guide, sized for a 20-gallon (76 L) tank, with enough for setup and a first refresh.

Or build it piece by piece. Start with the botanicals that belong there, then add jambolan as your tannin base:

• Climbing Swamp Fern
• Macaranga Leaves
• Melastoma Roots
• Organic Sphagnum Peat Moss
• Jambolan Leaves

This guide is for educational purposes. Always monitor water parameters and livestock behavior when adding botanicals. Botanicals are for aquarium use only and not for human consumption. Preparation required before use.

Sources

1. Schindler, I. & Linke, H. (2013). Betta hendra: a new species of fighting fish (Teleostei: Osphronemidae) from Kalimantan Tengah (Borneo, Indonesia). Vertebrate Zoology 63(1): 35–40. doi:10.3897/vz.63.e31411. Type locality, habitat, water parameters, coloration, size, sympatry, and peatland loss figures.
2. FishBase: Betta hendra. Etymology, size, and distribution.
3. Seriously Fish: Betta hendra. Brine shrimp feeding caution.
4. IUCN Red List of Threatened Species: Betta hendra, Critically Endangered (Low, B. W., 2019). Summary on the Asian Species Action Partnership species page.
5. Priyadi, A., Lukman, Nur, B., Marzuqi, M., Said, D. S., Cindelaras, S., Murniasih, S., Permana, A., Quyến, N. N., Müller, T. & Budi, D. S. (2025). First Captive Breeding Report of Critically Endangered Wild Betta hendra. Aquatic Conservation: Marine and Freshwater Ecosystems 35(7): e70186. doi:10.1002/aqc.70186. Range size, captive water conditions, conditioning, spawning, parental care, and larval development.
6. Borneo Nature Foundation (September 3, 2026). Emergency Fire Update: Early September. Sebangau orangutan population and the 2026 fire season.
7. Plants of the World Online, Royal Botanic Gardens, Kew. Stenochlaena palustris. Native range, including Borneo.
8. Plants of the World Online, Royal Botanic Gardens, Kew. Macaranga triloba. Native range.
9. Mirmanto, E. (2010). Vegetation analyses of Sebangau peat swamp forest, Central Kalimantan. Biodiversitas 11: 82–88. Dominant tree families, including Myrtaceae.
10. Plants of the World Online, Royal Botanic Gardens, Kew. Syzygium cumini. Native range.
11. Rohmy, S., Priyadi, A., Cindelaras, S., Gunawan, Sutrisno, Permana, A., Amin, M. & Budi, D. S. (2026). Bioecology, Conservation Status and Breeding Efforts of Wild Betta Fish (Teleostei: Osphronemidae) in Kalimantan, Indonesia. Aquatic Conservation: Marine and Freshwater Ecosystems 36: e70399. doi:10.1002/aqc.70399. Habitat conditions, threats, related Sebangau species, and the role of hobbyist breeding.