Picture a miniature fish in a tuxedo gliding through tea-colored forest streams—that’s Betta albimarginata.

Known to aquarists as the white-edged betta, this species is endemic to eastern Borneo in Indonesia, where it lives in shaded, leaf-littered trickles under dense rainforest canopy. The water there is stained the color of brewed tea by tannins, softly acidic and quiet, with roots and branches forming a maze of hideouts. In this dim world, the fish’s crisp white fin edges and deep reds aren’t just beautiful—they’re signals that cut through brown water like neon.

Its name tells a story: “albi” for white, “marginata” for edged, a nod to the clean, contrasting trim on the males’ fins. Betta albimarginata is part of a small mouthbrooding lineage within the bettas, most closely associated with the equally celebrated Betta channoides. Where many bettas blow nests of bubbles, this one invests in parenting differently: after a graceful, looping embrace, the male collects the eggs and carries them in his mouth until fully formed young are ready to be released. Watch closely and you’ll see him gently “roll” the clutch from time to time, a careful steward in miniature.

Despite the “fighting fish” label attached to the genus, B. albimarginata is more shadow-stalker than scrapper, slipping between curled leaves and peeking from the edges of submerged branches. Those white fin margins are more than decoration; they’re a built-in billboard for courtship and territorial display in murky light, flashing like semaphore as rivals size each other up and pairs coordinate their dance.

Life in Borneo’s blackwater is specialized, and that’s both its magic and its vulnerability. The peat swamps and forest streams this species calls home are shrinking due to drainage, fires, mining, and conversion to agriculture. Local collection for the aquarium trade happens, but the larger story is habitat—when the forest goes, the soft, tannin-rich creeks go with it, and so do the creatures adapted to them.

A few other charming footnotes round out its character. Like all bettas, it’s a labyrinth fish, meaning it can gulp air at the surface—handy in warm, oxygen-poor backwaters. It stays petite, with a slender, athletic build that seems designed for weaving through leaf curls. And while it shares its range with other tiny forest-stream specialists, there’s nothing quite like that dapper, white-trimmed flourish when a male flares in the half-light—an elegant signature from a hidden world.