Sims' betta

Betta simorum

Also known as Simorum fighter, Green dragon betta

FreshwaterFish

Sims' betta (Betta simorum) — The Wet Spot Tropical Fish · Used with permission

Care at a glance

Temperature: 73–81°F (23–27°C)
pH: 4.0–6.0
Adult size: 3.5 in (9 cm)
Minimum tank: 20 gal (75 L)
Temperament: Mostly peaceful
Social behavior: Social
Tankmates: Tankmates with caution
Swim level: Middle
Difficulty: Medium
Breeding: Hard
Rarity: Rare
Origin: Jambi and Riau peat swamps, Sumatra, Indonesia
Family: Osphronemidae

Overview

Sims' betta is a large wild betta best kept as a single pair, or as a group only in a big, heavily planted tank with room for each fish to hold territory. It is mostly peaceful but should be mixed with tankmates carefully, as small or delicate fish can be intimidated and rival males will squabble; many keepers give it a species tank. Feed it well with meaty foods: small live and frozen items, insects, and good pellets. Give a pair a shaded, deep tank of around 75 liters with dense cover and a tight lid, since this fish is a strong jumper.

In the wild

It lives in peat-swamp forest in the Jambi and Riau provinces of Sumatra, among leaf litter in shallow, shaded blackwater that is extremely soft and acidic. Recreate that with a dim, tannin-dark tank, dark substrate, leaf litter, driftwood, and floating cover overhead. Keep the temperature between 23 and 27 C and the pH low, from 4.0 to 6.0. Peat filtration and botanicals help hold the acidity.

Good to know

Betta simorum belongs to the family Osphronemidae, the labyrinth fishes, which breathe air at the surface through an accessory organ. It is one of the larger wild bettas at around 9 centimeters and sits in the Betta bellica group, close to the slender betta but with a more sloping head and longer pelvic fins. Unlike the mouthbrooding bettas, it is a bubble-nester: the male builds a nest at the surface and tends the eggs, and breeding it is difficult.

Did you know

Its species name honours the Sim brothers, Singaporean aquarists active in the wild-betta world; the plural Latin ending packs both siblings into a single name.