Betta Macrostoma

Meet Betta Macrostoma, a true gem of Borneo that brings a touch of rainforest magic to your freshwater setup. This species is endemic to Brunei Darussalam and the northern tip of Sarawak, with distinct color and pattern variations across localities. If you treasure fauna with a story, this is the betta that invites you to explore how geography shapes beauty in your aquarium.

Conservation and provenance you can trust
Betta Macrostoma is listed on the IUCN Red List as Vulnerable (D2), reflecting its restricted range and the need for careful stewardship. Brunei export has faced restrictions, making most hobby specimens sourced from Sarawak, where export rules differ. Each locality — from the Mendarem River and Labi rainforest to the Baram district near Marudi — presents its own palette of coloration, so keeping separate populations in dedicated tanks helps preserve their unique heritage.

Natural habitat and water chemistry

In the wild, Betta Macrostoma favors still, shady pools at the tops of rainforest waterfalls. The substrate tends to be gravel and rocks with leaf litter, while water can be clear but slightly brown from dissolved humic substances. Expect very soft, low-mineral water with pH typically ranging from 4.4 to 5.7, and negligible dissolved minerals. In the same streams you may find Rasbora tubbi and a red-coloured Machrobrahium sp shrimp, which likely form part of the natural diet and ecological balance.

Tank setup and maintenance

For a pair, an aquarium with base measurements of 80 × 30 cm (or equivalent) is a solid starting point. Betta Macrostoma can thrive in a fully-decorated setup, though many breeders prefer a simple, easy-to-maintain environment without substrate. Use driftwood, roots, and branches to create shaded pockets and gentle microhabitats where the fish can retreat. If you’re sourcing wood, dried beech or oak can be used safely after removing bark. The key is to recreate the soft, dark, forest-water feel they’re adapted to, without drastic chemical swings or strong currents.

Behavior, diet, and care tips

These fish are typically observed as pairs or small groups in the wild, often occupying quiet sections of rivers. In captivity, offer a diet that mirrors their natural feeding on crustaceans; in addition to high-quality betta foods, include small Macrobrachium sp shrimp or similar meaty fare in moderation to support coloration and health. Because water in their native habitat is low in minerals and highly acidic, maintain stability by avoiding rapid pH shifts, frequent water chemistry changes, or overly filtration that can strip essential safety buffers.

Why Betta Macrostoma stands out

• Remarkable localization: distinct color and pattern differences by locality—each tank can celebrate a unique lineage.
• Endemic wonder: a true Borneo species that evokes rainforest terrain and the thrill of natural history in your living room.
• Conservation-forward keeping: awareness of its Vulnerable status and legal considerations around export informs responsible collecting and hobbyist choices.
• Practical size and pairing: up to 9–10 cm in length; a paired setup in an 80 × 30 cm tank fits comfortably, allowing natural behaviors without crowding.

Who this is ideal for

• Experienced aquarists who appreciate geographic variation and the story behind each fish.
• keepers who enjoy designing multiple, locality-specific displays to showcase color and pattern diversity.
• Collectors prepared to maintain soft, acidic water with careful monitoring to mimic their native rainforest pools.

Practical considerations and best practices

• Preserve locality integrity by housing different populations separately to maintain their unique coloration and patterns.
• Avoid strong filtration or abrupt water chemistry shifts; aim for a stable, soft, acidic environment.
• Leverage driftwood and leaf litter to create shading and microhabitats that reflect their natural preference for quiet, shaded pool areas.
• Prepare for a modest but striking display: expect 9–10 cm length and a calm, contemplative presence in the tank rather than overt schooling behavior.