The Wild Habitat
Peat swamps and forest streams across Borneo, Sumatra, peninsular Malaysia, southern Thailand, and Cambodia. Water is extremely soft (TDS under 30), highly acidic (pH 4.0–6.0), warm (75–85°F), and dark with tannins.
Vegetation: emergent reeds, fallen leaves, submerged tree roots. No conventional aquarium plants — most peat swamps have no submerged plants because of low light penetration.
Tank Setup
Tank size: 20-gallon long for a small biotope, 40-gallon for a community.
Substrate: fine dark sand or peat-bottom (1 inch peat under 1 inch sand).
Hardscape: dark driftwood (Mopani, Malaysian), thick leaf litter, Indian almond catkins.
Plants: minimal. Cryptocoryne nurii (rare), Bucephalandra (Borneo native), or none.
Water Chemistry
pH: 4.5–6.0 (true blackwater is below 5.0).
GH: 0–3.
KH: 0–1.
Use RO water + heavy botanicals. Tap water cannot achieve this.
Wild Betta Species
Betta imbellis (Peaceful betta): small, peaceful, can be kept in groups.
Betta smaragdina (Emerald betta): from Cambodia and Thailand.
Betta brownorum: tiny mouthbrooder, perfect for nano biotope.
Betta macrostoma: jewel of Borneo, expensive, demanding.
Betta unimaculata: large mouthbrooder, paludarium suitable.
Other Compatible Fish
Chocolate gourami (Sphaerichthys osphromenoides): Borneo blackwater specialist. Demanding.
Sparkling gourami (Trichopsis pumila): tiny labyrinth fish, makes croaking sounds.
Cherry barb (Puntius titteya): Sri Lankan but blackwater-tolerant.
Liquorice gourami (Parosphromenus): tiny, jewel-colored, demanding.
Pygmy rasbora (Boraras maculatus, brigittae): nano shoal.
Maintenance
Leaf litter replacement: monthly.
Water changes: 20% every 2 weeks with prepared RO + botanical water.
Test pH and TDS weekly — drift happens fast in low-buffer water.