Meet the Betta

Betta Gillfriend care rules: one betta per tank. Mirror or flare practice: one 2-minute session a day, with at least 2 rest days a week. Train: up to 10 minutes a week.

Bettas (Betta splendens), also called Siamese fighting fish, are one of the most popular aquarium fish in the world, and for good reason. They are bold, curious, and full of personality. This section covers where they come from, how their bodies work, how long they live, and how to tell males from females.

Tip: Almost everything about good betta care makes sense once you picture their home in the wild: warm, shallow, still, plant-filled water with lots of places to hide.

Natural history

Where bettas come from

Betta splendens is native to Southeast Asia. Thailand is the heart of its range (especially the central plains), and it is also reported from Cambodia, Laos and Vietnam.
Wild bettas live in shallow, slow-moving or still water: rice paddies, ponds, marshes, ditches, lagoons and flooded fields.
Dense plants at the water's edge give them cover from birds such as egrets, herons and kingfishers, and those plants also support the insects they eat.
Wild bettas are carnivores. Their natural diet is mostly mosquito larvae and other small aquatic insects.

What their wild water is like

A University of Florida (UF/IFAS) fact sheet summarises field measurements from one wild population in Thailand:

Measurement	Wild habitat (one Thai population)
Water temperature	Average about 29.9°C (86°F); range about 27–31.5°C
pH	Average about 5.5 (acidic)
Water depth	Average about 5 cm (2 in)
Dissolved oxygen	Often low, swinging from near zero to about 7.4 mg/L over the day
Density	About 1.7 fish per square metre

These are field numbers, not aquarium targets. In the aquarium we aim for stable, clean, warm water (see Water quality).

Domestication

People in Southeast Asia have kept and bred bettas for a very long time, at least 1,000 years by some estimates, originally for fighting contests.
In the 1800s bettas reached Europe, where breeders focused on beauty rather than aggression. Today there are many recognised tail types and colours (see Betta types).
Wild bettas are much plainer than pet-store bettas: usually dull brown or green with some red or blue, with short fins.
In the wild, Betta splendens is now listed as vulnerable. Threats include habitat loss, pollution, and interbreeding with released domestic fish.

Warning: Never release a betta (or any aquarium fish) into local waterways. It is harmful to wild ecosystems and usually fatal for the fish.

Anatomy

The labyrinth organ: bettas breathe air

Bettas are labyrinth fish (anabantoids). Above their gills they have paired chambers lined with folded, bony plates covered in breathing tissue. This is the labyrinth organ, and it lets them gulp air at the surface.

Bettas breathe both with their gills and by gulping air. Their gills are relatively small.
They must be able to reach the surface. Research summaries describe bettas as able to drown if they are kept from the surface.
This is why every betta tank needs an air gap between the water and the lid, and why resting spots near the surface (like a leaf hammock) are popular.

Warning: The labyrinth organ does not make bettas "fine in dirty water". It helps them survive low oxygen, but ammonia and nitrite still poison them. Clean water matters just as much for bettas as for any other fish.

Gills and opercula (gill covers)

The opercula are the hard gill covers on each side of the head. When a betta flares, it pushes these out and spreads the membrane underneath (often called the "beard").
Flaring is an energy-hungry display. While flaring, a betta takes in less oxygen through its gills and eventually has to surface for air. This is one reason flaring sessions should be short (see Enrichment and flare training).
Healthy gills are hidden under the covers. If you can see red, swollen or pale gill tissue sticking out, or one gill cover stays held open, that is a warning sign (see Gill flukes).

Fins

Fin	Where it is	What it does
Dorsal	Top of the back	Stability; raised in displays
Caudal (tail)	Rear	Main source of thrust; the fin that defines most tail types
Anal	Underside, from belly to tail	Stability; long and flowing in many males
Ventral (pelvic)	Pair of thin fins under the chest	Steering and balance; used in displays
Pectoral	Pair of clear fins behind the gills	Fine steering and hovering; they flutter constantly

Long-finned bettas (halfmoons, veiltails and so on) carry a lot of fin. Their fins tear more easily, and they tire in strong current.
Short-finned plakats are closer to wild bettas in shape. They are usually stronger, faster swimmers.

Other features

Lateral line: a row of sensory pores along each side that senses water movement.
Swim bladder: a gas-filled organ that controls buoyancy. Problems with it, or with things pressing on it such as a full gut, cause floating or sinking (see Swim bladder disorder).
Slime coat: the mucus layer on the skin is a real defence. It seals the body, helps with salt and water balance, and contains protective compounds. Rough handling, poor water and some chemicals damage it.

Lifespan

PetMD (vet-written) gives an average lifespan of 3–5 years with proper care.
A research colony at Columbia University describes the lifespan under laboratory conditions as around 2 years.
How long a betta lives depends a lot on genetics, how it was raised and shipped, and the care it gets at home. Stable warm water, clean water and sensible feeding give the best odds.

Tip: Store bettas are often already several months old when you buy them, so your fish's "age" may be older than the time you have had it.

Do tail type, colour or size change lifespan?

No published study gives a lifespan for any tail type, colour or the giant line. In this app every domestic betta form shows the same species figure, 3–5 years with good care.
Long fins: long, flowing fins tear easily and are prone to fin rot, which is linked to poor water quality and stress (Chewy, reviewed by a vet). Veiltails, halfmoons, rosetails, crowntails and dumbos benefit most from clean water, gentle flow and smooth decor. The Columbia research colony also noticed that fish older than about 1.5 years seemed more prone to fin rot.
Giants: no one has published lifespan data for giant bettas, so there is no evidence they live longer or shorter. One giant care guide suggests planning on about 2–4 years.
Wild species and hybrids: Betta imbellis can live up to about 5 years. Betta smaragdina and "alien" hybrids have little or no published data; hobby care sheets estimate 3–5 years.

Male vs female

Feature	Males	Females
Fins	Usually longer and showier (except plakats, where both sexes are short-finned)	Usually shorter
Body	Often slimmer and longer	Often rounder in the belly, generally somewhat smaller
Beard (opercular membrane)	Larger and more obvious	Present but smaller
Ovipositor ("egg spot")	Absent	A small white dot just behind the ventral fins, between them and the anal fin
Bubble nests	Males build them	Rarely
Breeding bars	No	Vertical bars may show when ready to spawn
Temperament	Very territorial towards other males	Can also be aggressive, including to other females

In plakats, males and females can look alike. The IBC standard describes female plakats as having the same general form as males but with shorter fins, broader bodies and a rounder belly.
Males are more aggressive towards other males than towards females, while females tend to be more aggressive towards other females.
Two males must never share a tank (see Tank mates).

Tip: Rip, our flounder's fish, is a male giant koi plakat. Giant plakats are a line bred for a much larger body than ordinary bettas. The IBC standard expects a giant male to have a body length of at least 6 cm, and a genetics study describes giants as about three times larger than wild-type fish. Bigger fish need more room, more food and extra care with water quality (see Tank setup).

Sources

Care guide by Betta Gillfriend (Bespok Labs, BC, Canada). It is general information, not vet advice. If your betta is sick, ask an aquatic vet.