Betta / Siamese fighting fish (Betta splendens) care guide

Quick facts

Adult size: 6 cm
Lifespan: can live up to 5 years; captive average 2-4 years; chain-store stock often shorter due to genetic and rearing issues
Tank zone: top
Temperament: semi-aggressive
Difficulty: beginner

Water parameters

Temperature: 24–28°C
pH: 6.5 to 7.5
Hardness: 1 to 15 dGH

Tank requirements

Minimum volume: 19 L
Minimum length: 30 cm
Flow: low
Lighting: dim preferred
Substrate: any
Hiding spots: needed
Lid: required - jumper

Feeding

Diet: carnivore, feeds primarily at the top.

Betta-specific pellets preferred over flake; supplement with frozen bloodworms or brine shrimp 1-2x per week. Don't overfeed; bettas overeat to the point of bloat.

Compatibility

Males cannot be housed together under any circumstances; they will fight to the death
Will attack fin-nippers (tetras, barbs) and may itself harass slow long-finned tankmates like guppies
Most reliable solo. Suitable community tankmates are limited: small peaceful shoalers like ember tetras, harlequins, or corydoras in 75 L tanks
Females can sometimes be kept in sororities of 5+, but this is high-risk and many keepers consider it cruel; we don't recommend it without serious experience

Habitat

Native to the shallow rice paddies, ponds, and slow streams of Thailand, Cambodia, Laos, and Vietnam. Wild bettas are dull brown-green with short fins; the elaborate colors and flowing finnage of modern bettas are entirely the result of selective breeding over centuries. The labyrinth organ allows them to breathe atmospheric air, which is an adaptation to oxygen-poor stagnant water, not an excuse for keeping them in tiny containers. Males are aggressively territorial toward other males. Females can sometimes be kept in groups (sororities) of 5+ in tanks of 60 L or more, though aggression varies by individual.

Breeding

Bubblenest builder. The male blows a raft of bubbles at the surface, then courts the female aggressively. Spawning involves the male wrapping around the female in an embrace under the nest; she releases eggs and the male fertilizes and places them in the bubblenest. The male guards the nest and picks up fallen eggs. Remove the female after spawning or the male may kill her. Eggs hatch in 24-48 hours. Fry are tiny and need infusoria, then baby brine shrimp. Males begin fighting at 3-4 months and must be separated into individual containers.

Common problems

Fin rot is the single most common betta disease, caused by poor water quality (small unheated, unfiltered bowls are the usual culprit). Clean warm water (26–28°C) prevents most cases. Velvet (Piscinoodinium) is the second most common; it shows as a gold or rust-colored dust on the body, best visible with a flashlight at an angle. Bloating and constipation from overfeeding dried food is extremely common; fast one day per week and offer frozen daphnia as a laxative. Despite marketing, bettas are not suited to vases, bowls, or unfiltered containers. A heated, filtered tank of at least 15–20 L is the minimum for long-term health.

Bioload

Bioload coefficient: 1.8 (moderate-bodied labyrinth fish, low activity, comparable per-cm to a small gourami).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.