Betta Fish Care Guide

The betta, or Siamese fighting fish (Betta splendens), is a small labyrinth fish from the shallow, warm, still waters of Southeast Asia. It breathes air at the surface, and males were bred for generations to fight. That makes one male on its own easy to keep, but two males in one tank a disaster. It suits a beginner willing to run a small heated tank and change water regularly.

Care requirements

Need	What to provide
Enclosure	Sources disagree. Welfare guidance asks for at least 4 gal (15 L), ideally 5+ gal (20 L), with a lid. An extension paper argues small containers are fine if the water is well managed (RSPCA Queensland; University of Florida IFAS)
Temperature	About 75°F (24°C), held steady by a submersible heater. Unheated, the room must stay at 72°F (22°C) or warmer (RSPCA Queensland; University of Florida IFAS)
Lighting	Normal aquarium light of 8–10 hours a day. Keep the tank out of direct sunlight (RSPCA; RSPCA Queensland)
Diet	Carnivore. Feed 2–3 quality pellets or granules once or twice a day, with bloodworms, brine shrimp or daphnia as extras (RSPCA Queensland; University of Florida IFAS)
Lifespan	Average 3–5 years, often cut short by poor care (RSPCA Queensland)
Social needs	Keep males alone. Females can share in groups of more than four. Any tankmates should be plain, short-finned, peaceful fish (RSPCA Queensland; University of Florida IFAS)
Legal notes	No common restrictions; check local rules.

Male vs female bettas

	Male	Female
Aggression	Flare and bite at any other male, aiming for fins and flanks	Less aggressive; dominance squabbles in small groups
Housing	Alone, or with peaceful, plain, short-finned fish	In groups of more than four, so aggression is spread out
How farms keep them	Separated by 3–4 months old to prevent injury	Reared in communal tanks

Sources: University of Florida IFAS; RSPCA Queensland.

How big a tank? The honest answer

This is the most argued-over point in betta keeping, and welfare bodies and researchers disagree.

• University of Florida IFAS says bettas evolved in shallow, warm, low-oxygen water, often only about 2 in (5 cm) deep. In one study cited in the paper, males grew better in 150 ml of water than in 300 ml. Its view is that water quality depends on management, not container size: a small bowl works if you change the water often.
• RSPCA Queensland says bettas need “a minimum of 15 litres of water, although 20 or more is ideal” (about 4–5+ gal) to meet their behavioural needs. It also calls the tiny-bowl-and-lamp idea incorrect.
• The RSPCA (UK) recommends no aquarium smaller than 45 × 30 × 30 cm (about 18 × 12 × 12 in, 40 L or roughly 10 gal) for any fish. It says larger volumes hold temperature and water quality more steadily.

A reasonable reading is a range: 4 gal (15 L) as a floor, and 5–10 gal (20–40 L) gives more stability and more room for plants. Whatever the size, cover the tank with a lid, because bettas jump. Leave an air gap under the lid so the fish can breathe at the surface (RSPCA Queensland).

Heat, flow and water changes

Wild bettas live in water at about 81–89°F (27–31.5°C) (University of Florida IFAS). RSPCA Queensland recommends about 75°F (24°C) and a submersible heater for a steady temperature. University of Florida IFAS warns that bettas “do not do well in cold water”. Without a heater, the room must stay at 72°F (22°C) or warmer, which most homes can’t guarantee overnight or in winter. Use a heater with a built-in thermostat and check a thermometer daily (RSPCA).

Bettas prefer calm water. Research cited by University of Florida IFAS used water flow as a stressor, and the paper notes that heavy filtration can harm a betta. Use a filter with adjustable flow, or a sponge filter, set low (RSPCA Queensland). Change about 10% of the water weekly with a gravel vacuum (RSPCA Queensland). Small or unfiltered tanks need more frequent changes so ammonia never builds up (University of Florida IFAS). Dechlorinate new water and match its temperature before adding it (RSPCA).

Gotchas

• Two males in one tank, or a male with a mirror. Males flare and then bite each other’s fins and flanks. A mirror triggers the same flaring until the fish is exhausted (University of Florida IFAS; RSPCA Queensland).
• Showy tankmates. RSPCA Queensland advises keeping only plain, short-finned species with a male. Long-finned, colourful fish are likely to be treated as rivals.
• No heater in a cool room. Below 72°F (22°C) a betta does poorly (University of Florida IFAS). A desk lamp is not a heater.
• Sharp decor and plastic plants. Long fins tear easily. RSPCA Queensland advises smooth ornaments only, plus plants that reach near the surface so the fish has resting spots.
• Overfeeding. Uneaten pellets foul a small volume of water quickly. Two or three pellets per feed is enough (RSPCA Queensland).

Avoid

• Mirrors and constant views of another male
• Strong filter currents and powerful air stones
• Unheated bowls in rooms that drop below 72°F (22°C)
• Rough or sharp ornaments and decorations that snag fins
• Placing the tank in direct sunlight (RSPCA Queensland)
• Untreated tap water: chlorine harms fish (RSPCA)
• Very heavy-tailed strains such as “rose-tailed” bettas. The RSPCA warns their fins can cause health problems.

Signs to see a vet

Watch for fins that are ragged, clamped or shrinking, white spots, open sores, a sunken belly, or a fish that sits on the bottom and stops eating (RSPCA). Check temperature and test ammonia first. If the water is fine, University of Florida IFAS advises seeing a fish veterinarian rather than guessing at treatments, because many medications do more harm than good when used wrongly.