Betta
Also known as Siamese fighting fish, Betta splendens
- Adult size
- About 6–7 cm, plus fins
- Lifespan
- 2–5 years
- Origin
- Thailand and neighbouring parts of South-East Asia, including Cambodia, Laos and Vietnam
- Company
- Males must live alone or with carefully chosen peaceful tank mates
- Curious
- Territorial
- Colourful
- Interactive
About the Betta
The betta is one of the most recognisable aquarium fish in the world, prized for the flowing fins and jewel colours that centuries of selective breeding have produced. Wild bettas are far plainer, short-finned fish that live in shallow, slow-moving and heavily planted waters such as rice paddies, ditches and marshes.
Bettas have a labyrinth organ that lets them gulp air from the surface, which helps them survive in oxygen-poor water. Sadly this ability has fed the idea that they can live in tiny cups or vases, when in reality they do best in a properly heated, filtered aquarium.
Kept well, a betta is an inquisitive, personable fish that will often come to the front of the tank to greet its owner. Males build bubble nests at the surface, which is a normal behaviour rather than a sign of anything wrong.
Temperament
Male bettas are famously aggressive towards one another and will fight, often to serious injury, so two males must never share a tank. Some males also attack fish with long fins or bright colours that resemble a rival. Individual personalities vary widely: some bettas live peacefully alongside small, calm bottom-dwellers or snails, while others will not tolerate any company. Females can also be territorial, and keeping groups of females is best left to experienced keepers.
Tank & water
A single betta needs a heated, filtered tank of at least around 20 litres, and more room makes stable water much easier to maintain. Keep the water at roughly 24–28°C with a reliable heater, since bettas are tropical fish and become sluggish and prone to illness when cold. Choose a gentle filter or baffle the outflow, because the long fins of fancy varieties make swimming against a strong current exhausting. Live or soft silk plants, floating leaves to rest under and a well-fitting lid (bettas can jump) complete the set-up. Cycle the tank fully before the fish goes in.
Diet
Bettas are carnivores that naturally eat insects and their larvae, so a good-quality betta pellet or flake should form the basis of the diet. Small frozen or live foods such as bloodworm, brine shrimp and daphnia make useful treats a few times a week. Feed only what is eaten within a minute or two, once or twice a day, because overfeeding is a common cause of bloating and fouled water.
Behaviour & tank mates
Bettas explore their surroundings constantly and benefit from a varied layout with plants, caves and leaves near the surface where they like to rest. Rearranging decor occasionally and offering live foods to hunt can keep them active. Brief sessions with a mirror are sometimes used to encourage flaring, but this is stressful if overdone and should be kept to a few seconds at most. If tank mates are added, choose very peaceful, short-finned species and have a back-up plan in case the betta turns aggressive.
Tank maintenance
Change around a quarter of the water each week using dechlorinated water at the same temperature, and vacuum waste from the gravel. Rinse filter media in old tank water rather than tap water so the beneficial bacteria survive.
Health
Fin rot, where fin edges become ragged, discoloured or shortened, is very common in bettas and is usually linked to poor water quality. Bettas are also prone to white spot, velvet (a fine gold or rust-coloured dusting), bloating and swim bladder problems from overfeeding, and dropsy, in which the body swells and scales stick out like a pine cone. Testing the water should always be the first step when a betta seems unwell, followed by advice from an aquatic vet or experienced aquatic specialist.
Prone to
- Fin rot
- White spot (ich)
- Velvet
- Swim bladder problems
- Dropsy
- Constipation and bloating
Call a vet if you notice
- Gasping at the surface far more than usual or lying on the bottom — test the waterEmergency
- Fins rapidly shrinking, blackened or with white edges
- Scales lifting outwards like a pine cone
- A gold or rusty dust on the body
- Refusing food for more than a few days
- Clamped fins and dull colour that do not improve after a water change
An aquatic vet or experienced aquatic specialist is best placed to help. Find one before you need them.
Common questions
Can a betta live in a bowl?
Bettas can survive for a while in a bowl, but they do not thrive in one. Small, unheated, unfiltered containers quickly build up toxic waste and get too cold. A heated, filtered tank of at least around 20 litres is the kinder option.
Why is my betta making bubbles at the surface?
This is a bubble nest, which male bettas build to hold eggs during breeding. It is a normal behaviour and often a sign the fish feels settled, even when no female is present.
Can two bettas live together?
Two males should never share a tank, as they will fight. Males and females should only be put together briefly for planned breeding by experienced keepers, as the male can injure the female.
Why are my betta's fins falling apart?
Ragged, shrinking fins are often fin rot, which is usually triggered by poor water quality, though some bettas also bite their own fins when stressed. Test the water, carry out a partial water change and seek advice from an aquatic vet or specialist if it continues.
Written by the Petopedia editorial team to our editorial standards. General guidance, not veterinary advice.