Siamese fighting fish

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Siamese fighting fish or betta
HM Orange M Sarawut.jpg
Selectively bred halfmoon male displaying his flared opercula.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Osteichthyes
Subclass: Actinopterygii
Superorder: Acanthopterygii
Order: Perciformes
Family: Osphronemidae
Subfamily: Macropodusinae
Genus: Betta
Species: B. splendens
Binomial name
Betta splendens
Regan, 1910

The Siamese fighting fish (Betta splendens), also sometimes colloquially known as the Betta, is a species in the Gourami family which is popular as an aquarium fish. They are called pla-kad (biting fish) in Thai or trey krem in Khmer. They are a highly aggressive fish and it is unwise to house two males together - and even the females may kill each other. They can do well with calm, dully-colored bottom-dwelling species such as Corydoras catfish. Steer clear of other popular freshwater tankmates such as African Dwarf or Clawed Frogs, as they have poor eyesight and can mistake the Betta's flowing tail for a worm or other prey; even small tetras will nip if not kept in a large enough school.

These species are native to the Mekong basin of Laos, Cambodia, Vietnam and Thailand The fish can be found in vast standing waters of canals, rice paddies and floodplains.[1]

In January 2014 a large population of the fish was discovered in the Adelaide River Floodplain in the Northern Territory, Australia.[2] As an invasive species they pose a threat to native fish, frogs and other wildlife in the wetlands.[2]


B. splendens usually grows to a length of about 6.5 cm (2.6 in).[1] Although aquarium specimens are known for their brilliant colors and large and typically flowing fins, the natural coloration of B. splendens are generally dull green, brown and gray, and the fins of wild specimens are short, about the size of the B. Splendens plakat tail. In captivity, they have been seen with varying fin sizes and varieties and as well as observed coming in colors such as salamander, mustard gas, butterfly, blue, red, white, black and many others.


Betta splendens in the wild feed on Zooplankton, Crustaceans, and the larvae of mosquitoes and other water-bound insects.[3] However, in captivity they can be fed a steady diet of pellets and frozen foods such as brine shrimp, bloodworms, daphnia and many others.

Despite myths that they will feed on any plant matter in the tank, they are naturally insectivores and would typically never eat vegetation as it is not natural for them to do so.

Reproduction and early development[edit]

A pair spawning under a bubble nest in a breeder's tank
One-day-old larvae in a bubble nest, their yolk sacs have not yet been absorbed: Betta fry rely entirely on their gills to breathe.
Betta splendens fish build bubble nests of varying sizes.
A 15-day-old, free-swimming fry is infected with Piscinoodinium sp. (velvet disease), a common killer of betta fry in captivity.

Male Betta will flare their gills, spread their fins and twist their bodies in a dance if interested in a female. If the female is also interested she will darken in color and develop horizontal lines known as breeding bars as a response. Males build bubble nests of various sizes and thicknesses at the surface of the water. Most tend to do this regularly even if there is no female present.

Plants or rocks that break the surface often form a base for bubble nests. The act of spawning itself is called a "nuptial embrace", for the male wraps his body around the female; around 10–40 eggs are released during each embrace, until the female is exhausted of eggs. The male, in his turn, releases milt into the water, and fertilization takes place externally. During and after spawning, the male uses his mouth to retrieve sinking eggs and deposit them in the bubble nest (during mating the female sometimes assists her partner, but more often she simply devours all the eggs she manages to catch). Once the female has released all of her eggs, she is chased away from the male's territory, as she will likely eat the eggs.[4] If she is not removed from the tank then she will most likely be killed by the male.

The eggs will remain in the males care. He carefully keeps them in his bubble nest, making sure none falls to the bottom, repairing the bubble nest as needed. Incubation lasts for 24–36 hours; newly hatched larvae remain in the nest for the next two to three days until their yolk sacs are fully absorbed. Afterwards, the fry leave the nest and the free-swimming stage begins. In this first period of their lives, B. splendens fry are totally dependent on their gills; the labyrinth organ which allows the species to breathe atmospheric oxygen typically develops at three to six weeks of age, depending on the general growth rate, which can be highly variable. B. splendens can reach sexual maturity at an age as early as 4–5 months.


Some people of Thailand and Malaysia are known to have collected these fishes prior to the 19th century from the wild.

In the wild, betta spar for only a few minutes or before one fish backs off. Bred specifically for heightened aggression for fighting, domesticated betta matches can go on for much longer, with winners determined by a willingness to continue fighting. Once a fish retreats, the match is over.

Seeing the popularity of these fights, the king of Thailand started licensing and collecting these fighting fish. In 1840, he gave some of his prized fish to a man who, in turn, gave them to Dr. Theodor Cantor, a medical scientist. Nine years later, Dr. Cantor wrote an article describing them under the name Macropodus pugnax. In 1909, the ichthyologist Charles Tate Regan, realizing a species was already named Macropodus pugnax, renamed the domesticated Siamese fighting fish Betta splendens.[5]

1892 this species was imported to France by the French aquarium fish importer Pierre Carbonnier in Paris, and 1896 the German aquarium fish importer Paul Matte in Berlin, imported the first specimens to Germany from Moscow.[6]

In the aquarium[edit]


Betta species prefer a water temperature of around 23–27 °C (73.4-80.6 °F) but have been seen to survive at the extremes of 20 and 30 °C (68 and 86 °F) though their life quality may be diminished at these extremes of the betta's tolerance. Bettas are also affected by the pH levels of the water they are kept in. Most ideal levels for Bettas would be at a neutral pH (7.0) However, Bettas are slightly tolerant towards the pH levels.[7] They have an organ known as the labyrinth organ which allows them to breathe air at the water's surface. This organ was thought to allow the fish to be kept in unmaintained aquaria,[8] but this is a misconception, as poor water quality makes all tropical fish, including Betta splendens, more susceptible to diseases such as fin rot.

Properly kept and fed a correct diet, Siamese fighting fish generally live between 3–5 years in captivity, but may live between 7–10 years in rare cases.[citation needed]

Aquarium Size[edit]

It is popular to keep betta fish in very small containers for display around the home. Contrary to popular belief this can stress the fish causing health issues. Bettas prefer to be kept in larger tanks or community tanks. The smallest tank recommended is 5 gallons (20 litres), and bigger is always better.[9] Do not keep more than one male in the tank as they will likely fight and kill one another.


B. splendens can be hybridized with B. imbellis, B. mahachaiensis, and B. smaragdina, though with the latter, the fry tend to have low survival rates. In addition to these hybrids within the Betta genus, intergeneric hybridizing of Betta splendens and Macropodus opercularis, the paradise fish, has been reported. A fairly recent variety to hit the markets is the king betta, a variety of largely unknown provenance which may or may not be derived from crossing B. splendens with B. raja.[10][unreliable source?]

Breeders around the world continue to develop new varieties. Often, the males of the species are sold preferentially in stores because of their beauty, compared to the females. Recently, breeders have developed in females the same range of colours previously only bred in males.[citation needed] Females almost never develop fins as showy as males of the same type and are often more subdued in coloration, though some breeders manage to get females with fairly long fins and bright colours.


A dalmatian orange male

Wild fish exhibit strong colours only when agitated.[citation needed] Breeders have been able to make this coloration permanent, and a wide variety of hues breed true. Colours available to the aquarist include red, orange, yellow, blue, steel blue, turquoise/green, black, pastel, white ("opaque" white, not to be confused with albino), and multi-coloured fish. The shades of blue, turquoise, and green are slightly iridescent, and can appear to change colour with different lighting conditions or viewing angles; this is because these colours (unlike black or red) are not due to pigments, but created through refraction within a layer of translucent guanine crystals. Breeders have also developed different colour patterns such as marble and butterfly, as well as metallic shades through hybridization[11] like copper, gold, or platinum (these were obtained by crossing B. splendens to other Betta species).

Purple and blue female

A true albino betta has been feverishly sought since one recorded appearance in 1927, and another in 1953 .[citation needed] Neither of these was able to establish a line of true albinos. In 1994, a hobbyist named Kenjiro Tanaka claimed to have successfully bred albino bettas.[12]

Some bettas will change colours throughout their lifetime (known as marbling), attributed to a transposon.[13]

Common Colours[14]

  • Red
  • Blue
  • Green
  • Yellow
  • Opaque
  • Black
  • White
  • Albino
  • Orange

Interesting Colours[14]

  • Metallic
  • Turquoise
  • Copper
  • Lavender
  • Mustard Gas
  • Grizzle
  • Kois
  • Marble

Colour Patterns[14][edit]

  • Solid - The entire fish is one colour with no variations
  • Bi-Color - The fins must be a different colour to the body to be a Bi-Colour.
  • Cambodian - The body is pale, almost colourless, and the fins are a solid colour
  • Butterfly - The fins have distinct bands of colours
  • Marble - Irregular patterns throughout the body and fin
  • Piebald - pale flesh-coloured face no matter what the body colour is
  • Full Mask - the face being the same colour as the body rather than what it would naturally be which would be darker than the body
  • Dragon - rich strong base colour with the scales on the main part of the body a pale iridescent
  • Multicolour - 3 or more colours on the body that does not fit into any other pattern category
  • Fancy

Finnage variations[14][edit]

A metallic, double-tail male
A crowntail male

Breeders have developed several different finnage and scale variations:

  • Veil tail (extended finnage length and non-symmetrical tail; caudal fin rays usually only split once) the most common tail type seen in pet stores.
  • Crown tail (fin rays are extended well beyond the membrane and consequently the tail can take on the appearance of a crown; also called fringetail)
  • Comb tail (less extended version of the crown tail, derived from breeding crown and another finnage type)
  • Half-moon ("D" shaped caudal fin that forms a 180° angle, the edges of the tail are crisp and straight)
  • Over-half-moon (caudal fin is in excess of the 180° angle, byproduct of trying to breed half-moons, can sometimes cause problems because the fins are too big for the fish to swim properly)
  • Rose tail (halfmoon variation with so much finnage that it overlaps and looks like a rose)
  • Feather tail (similar to the rose tail, with a rougher appearance)
  • Short-finned fighting style (sometimes called "plakat")
  • Half-moon plakat (short-finned half-moon, plakat and half-moon cross)
  • Double tail (the tail fin is duplicated into two lobes and the dorsal fin is significantly elongated, the two tails can show different levels of bifurcation depending on the individual)
  • Delta tail (tail spread less than that of a half-moon with sharp edges)
  • Half-sun (combtail with caudal fin going 180°, like a half-moon)
  • Elephant ear (pectoral fins are white, and much larger than normal, resembling the ears of an elephant)
  • Spade tail (caudal fin has a wide base that narrows to a small point)


A male attacking and flaring at his reflection in a mirror.

Males and females flare or puff out their gill covers (opercula) to appear more impressive, either to intimidate other rivals or as an act of courtship. Other reasons for flaring are when they are startled by movement or change of scene in their environments. Both sexes display horizontal bars (unless they are too light a colour for this to show) if stressed or frightened. However, such colour changes, common in females of any age, are very rare in mature males. Females often flare at other females, especially when setting up a pecking order. Flirting fish behave similarly, with vertical instead of horizontal stripes indicating a willingness and readiness to breed (females only). In fact, the fish flare their fins and gill covers as a sign of aggression or flirting with other fish. Bettas sometimes require a place to hide, even in the absence of threats. They may set up a territory centered on a plant or rocky alcove, sometimes becoming highly possessive of it and aggressive toward trespassing rivals.

Contrary to popular belief, Bettas are compatible with many other species of aquarium fish.[15] Bettas are known to be more aggressive towards smaller fishes that resemble them, than larger ones like Loaches and Clown Plecos that they can clearly distinguish as other species. In general, they're also less aggressive towards fishes that are less colourful and vivid.[16]

The aggression of this fish has been studied by ethologists and comparative psychologists.[17] These fish have historically been the objects of gambling; two male fish are pitted against each other in a fight and bets are placed on which one will win. One fish is almost always killed as a result. To avoid this, male Siamese fighting fish are best isolated from one another. Males will occasionally even respond aggressively to their own reflections in a mirror. Though this is obviously safer than exposing the fish to another male, prolonged sight of their reflection might lead to stress in some individuals. Not all Siamese fighting fish respond negatively to other male fish, especially if not too many of them are present.[citation needed]

Several females in a community tank with mollies and rainbowfish


Although commonly called a betta in the aquarium trade, especially in North America, that is the name of a genus not only containing this fish, but also other species. B. splendens is more accurately called by its scientific name or "Siamese fighting fish", to avoid confusion with the other species in the genus.

In popular culture[edit]

  • In the 1963 James Bond movie From Russia with Love, the strategy of the criminal organization SPECTRE is compared to three Siamese fighting fish in the same tank: Two will fight each other to the death while the third will wait its turn to fight the exhausted victor, symbolizing the conflict between the USA and the Soviet Union, with SPECTRE as the fish that waits.
  • The title of S.E. Hinton's 1975 novel, Rumble Fish, is an eponymous reference to what two brothers call the breed. In Francis Ford Coppola's 1983 film adaptation, everything appears in black and white except the Siamese fighting fish.
  • In 2005, Dianne Gremillion publishes a children's book titled A Fish Named Matroly about a beautiful betta fish who needs a home, but ends up finding more than a home when it ends up befriending a young boy named Zachary who ends up learning all the How-Tos of caring for betta fish.
  • A 2006 episode of Cold Case ("Saving Sammy") features a boy with a pet Siamese fighting fish.
  • The Siamese fighting fish has been used as the default background in the beta and release candidate versions of the 2009 Windows 7 operating system, in an apparent reference to the name "Betta". A similar wallpaper and boot screen also was used in the pre-releases of Windows 8.
  • A Siamese fighting fish features as a clue in a murder in the 2009 film Bad Lieutenant: Port of Call New Orleans.
  • Milo, one of the main characters in the Disney Channel's 2010 series, Fish Hooks, is a Siamese fighting fish.
  • Meet Mindy The Betta Fish is a 2012 e-Book by Rema R. Kenton geared towards children.
  • In the BBC children's series M.I. High, the plot of one episode involves causing the children to have their minds altered to that of a fighting fish by use of brainwaves distributed in a Van de Graaff generator.
  • In a season 4 episode of FX's animated series "Archer" ("Live And Let Dine") character Pam Poovey is shown to have a pet Siamese fighting fish named Germaine. Although she is quite attached to him, he is proven to be very poor at his job, (illegal fish fighting) having driven Pam $14,000 into debt.
  • A Siamese fighting fish named Juice Lee is featured in "To the Rescue (Part 2)", an episode of Chip 'n Dale Rescue Rangers.
  • In USA Network's series "Mr. Robot", character Elliot Alderson has a pet betta fish. In the first season, fourth episode (eps1.3), the fish seemingly speaks aloud to him in his hallucination, and later in the hallucination, is served to him and his friend Angela on a platter.
  • The Incredibly True Adventures of CLYDE the Betta Fish is a 2015 e-Book by T. Torrest geared towards children.
  • Used by Apple in 2015 for promotional media for the IPhone 6S.


  1. ^ a b Froese, Rainer and Pauly, Daniel, eds. (2014). "Betta splendens" in FishBase. February 2014 version.
  2. ^ a b Bray, Dianne. "Siamese Fighting Fish, Betta splendens". Fishes of Australia. Retrieved 29 September 2014. 
  3. ^ "betta food". Retrieved 2012-08-01. 
  4. ^ Leong, Paul (2004). Tips on Spawning Bubblenesting Bettas. Retrieved on March 13, 2009.
  5. ^ "Betta Origins". Betta Fish Center. Retrieved 11 June 2011. 
  6. ^ "Betta splendens -article-". 
  7. ^ "betta water". Retrieved 2015-10-05. 
  8. ^ Caller, Steven. "Betta Fish Introduction". My Betta Fish. Retrieved 2012-08-01. 
  9. ^
  10. ^ Juniper Russo (2009): "King Betta" Variety Sold at Petco
  11. ^ "Metallics and Masked". Betty
  12. ^ "Albino image". Retrieved 2012-08-01. 
  13. ^
  14. ^ a b c d "Colors & Patterns". Retrieved 2015-10-04. 
  15. ^ "7 Excellent Betta Tank Mates for Your Siamese Fighting Fish". Retrieved 2015-08-20. 
  16. ^ "Betta Fish Facts". Retrieved 2015-08-20. 
  17. ^ Bronstein, Paul M. (1998). "Agonistic Sequences and the Assessment of Opponents in Male Betta splendens". American Journal of Psychology 265 (2): 163–177. JSTOR 1422809. 

Further reading[edit]

  • Simpson, M. J. A. (1968). "The display of the Siamese fighting fish Betta splendens". Animal Behaviour Monographs 1: 1–73. 
  • Thompson, T (1966). "Operant and Classically-Conditioned Aggressive Behavior in Siamese Fighting Fish". American Zoologist 6: 629–741. doi:10.1093/icb/6.4.629. 

External links[edit]