B. splendens usually grows to a length of about 7 cm (2.8 in). Although aquarium specimens are widely known for their brilliant colors and large, flowing fins, the natural coloration of B. splendens is generally green, brown and grey, and the fins of wild specimens are short. In the wild, they exhibit strong colors only when agitated. In captivity, they have been selectively bred to display a vibrant array of colors and tail types.

Conservation status

Although popular as an aquarium fish, the IUCN has classified B. splendens in the vulnerable category. The fish is naturally endemic to Thailand and can be found in shallow areas in marshes or paddy fields. The primary threat is due to habitat destruction and pollution, as farmlands continue to be developed across central Thailand.

Diet

Cockatiels are relatively vocal birds, the calls of the male being more varied than that of the female. Cockatiels can be taught to sing specific melodies and speak many words and phrases.

Male bettas 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 vertical 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.[9] If she is not removed from the tank then she will most likely be killed by the male.

The eggs will remain in the male's care. He carefully keeps them in his bubble nest, making sure none fall 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.

water

Betta species prefer a water temperature of around 75-82 degree F (24-28 degreeC) but have been seen to survive temporarily at the extremes of 56 degreeF (13 degreeC) or 95 degreeF (35 degreeC). When kept in colder climates, aquarium heaters are recommended.

Bettas are also affected by the pH levels of the water. Ideal levels for Bettas would be at a neutral pH (7.0) However, Bettas are slightly tolerant towards the pH levels. 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, 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 and 5 years in captivity, but may live between 7 and 10 years in rare cases.

Aquarium size and cohabitants

The minimum tank size is directly related to how experienced the fish keeper is, and how often they want to carry out water changes, in order to keep the water pristine. The Betta must of course have enough room to turn around, but there is no evidence that they require a lot of space. Due to their labyrinth organ they are not dependent on high oxygen levels in the water, so a large surface area for gas exchange is not required. Some Betta enthusiasts claim that there is a minimum tank size for a Betta, but to try to set a strict baseline minimum is somewhat arbitrary. Reliably performing regular partial water changes (every other day for small unfiltered tanks) would at least ensure the water quality in a smaller tank is acceptable. Most consider 9 to 19 litres (2.5 - 5 US gallons) to be an ideal tank size for a Betta, "but you can successfully keep a Betta in a 4 litre (1 gallon) tank provided you clean it regularly" and maintain an acceptable temperature (generally 24degreeC to 26degreeC - 75F to 78F - is considered optimal).

Bettas can cohabit with fish that are bottom feeders, however it is not advised to keep them with feeders that may eat their fins or destroy the slime coat (one example is the Siamese Algae Eater, if kept in an inappropriately sized tank)

Varieties

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 genus Betta, intergeneric hybridizing of Betta splendens and Macropodus opercularis, the paradise fish, has been reported.

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. 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 colors.

Wild fish exhibit strong colours only when agitated. 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 like copper, gold, or platinum (these were obtained by crossing B. splendens to other Betta species).

Bettas are found in many different colours due to different layers of pigmentation in their skin. The layers (from furthest within to the outer layer) consists of red, yellow, black, iridescent (blue and green), and metallic (not a colour of its own, but reacts with the other colours to change how they are perceived). Any combination of these layers can be present, leading to a wide variety of colours.

A true albino betta has been feverishly sought since one recorded appearance in 1927, and another in 1953. 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. Some bettas will change colours throughout their lifetime (known as marbling), attributed to a transposon. Koi bettas have mutated now and some are no longer marbles and do not change colors or patterns through out their lifetime (known as true Koi) attributed to the defective gene that causes marbling not being repaired in the color layers after a time

common colors

• Super Red
• Super Blue
• Super Yellow
• Opaque
• Super Black
• Super White
• Orange
• Marble
• Candy
• Nemo
• Galaxy Nemo
• Koi
• Alien
• Copper
• Cellophane
• Gold
• Galaxy Koi

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 can include when they are intimidated by movement or change of scene in their environments. Both sexes display pale horizontal bars if stressed or frightened. However, such colour changes, common in females of any age, are rare in mature males due to their intensity of colour. 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). Betta splendens enjoy a decorated tank, being a territorial fish it is necessary to establish territory even when housed alone. They may set up a territory centered on a plant or rocky alcove, sometimes becoming highly possessive of it and aggressive toward trespassing rivals. This is the reason why when kept with other fish the minimum tank size should be 45 litres (about 10 gallons). Contrary to popular belief, bettas are compatible with many other species of aquarium fish. Given the proper parameters bettas will be known to only be aggressive towards smaller and slower fish than themselves such as guppies.

The aggression of this fish has been studied by ethologists and comparative psychologists. These fish have historically been the objects of gambling; two male fish are pitted against each other to fight and bets are placed on which one will win. One fish will arise the victor, the fight continuing until one participant is submissive. These competitions can result in the death of either one or both fish depending on the seriousness of their injuries. To avoid fights over territory, 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 may lead to stress in some individuals. Not all Siamese fighting fish respond negatively to other males, especially when the tank is large enough for each fish to create their own designated territory.[

Aggressive behavior in females

In general, studies have shown that females exhibit similar aggressive behaviors as their male counterparts, but these behaviors are less common.[30] A group of female Siamese fighting fish were observed over a period of two weeks. During these two weeks, the following behaviors were recorded: attacking, displays, and biting food. The results of this observational study indicated that when females are housed in small groups, they form a stable dominance order. For example, the fish who was ranked at the top showed higher levels of mutual displays, in comparison to the fish who were of lower ranks. The researchers also found that the duration of the displays differed depending on whether an attack occurred. The results of these studies indicate that female Siamese fighting fish should be considered as often as males, as there are evidently interesting variations in their behaviors as well.

Metabolic costs of aggression

Studies have found that Siamese fighting fish often begin with behaviors that require high cost, and gradually decrease their behaviors as the encounter proceeds. This indicates that Siamese fighting fish will first begin an encounter using much metabolic energy, but will gradually decrease, as to not use too much energy, thus making the encounter a waste if the fish is not successful. Similarly, researchers have found that when pairs of male Siamese fighting fish were kept together in the same tank for a three-day period, aggressive behavior was most prevalent during the mornings of the first two days of their cohabitation. However the researchers observed that the fighting between the two males decreased as the day progressed. The male in the dominant position initially had metabolic advantage; although as the experiment progressed, both fish became equal in regards to metabolic advantages.[35] In regards to oxygen consumption, one study found that when two male Siamese fighting fish fought, the metabolic rates of both fish did not differ before or during the fight. However, the fish who won showed higher oxygen consumption during the evening subsequent to the fight. Therefore, the results of this study indicate that aggressive behavior in the form of fighting has long-lasting effects on metabolism.

Courtship behavior

There has been numerous research in the area of courtship behavior between male and female Siamese fighting fish. This research has focused on the aggressive behaviors of males during the courtship process. For example, one study found that when male fish are in the bubble nest phase, their aggression toward females is quite low. This is due to the males attempting to attract potential mates to their nest, so eggs can successfully be laid. It has also been found that in regards to mate choice, females often “eavesdrop” on pairs of male Siamese fighting fish while they are fighting. When females witness aggressive behavior between a pair of males, the female is more likely to be attracted to the male who won. In contrast, if a female did not “eavesdrop” on aggressive behavior between a pair of males, the female will show no preference in mate choice. In regards to the male fish, the “loser” fish are more likely to attempt to court the fish who did not “eavesdrop”. The “winner” fish have been found to show no preference in regards to female fish who “eavesdropped” and those who did not.

One study considered the ways in which male Siamese fighting fish alter their behaviors during courtship when another male is present. During this experiment, a dummy female was placed in the tank. The researchers expected that males would conceal their courtship from intruders, however this surprisingly was not the case. It was found that when another male fish was present, the male was more likely to engage in courtship behaviors with the dummy female fish. When no barriers were present, the males were more likely to engage in gill flaring at an intruder male fish. Therefore, the researchers conclude that the male is attempting to court the female and communicate with the rival male present at the same time. These results indicate the importance of considering courtship behavior, as the literature has suggested there are many factors that can dramatically affect the ways in which both male and females can act in courtship settings.

Effects of chemical exposure on behavior

Chemicals such as hormones can have powerful effects on the behavior of an individual. Researchers have considered the effect that such chemicals can have on Siamese fighting fish. This section will examine three studies, each of which indicates that chemicals can significantly affect the behaviors of Siamese fighting fish. In particular, these behavior changes are most likely to occur in regards to aggression.

One study investigated the effect of testosterone on female Siamese fighting fish. Females were first given testosterone, which resulted in physical changes. This included fin length, body coloration and gonads. These physical changes resulted in the females resembling typical male fish. Next their aggressive behavior was monitored. It was found that when these females interacted with other females, their aggression increased. In contrast, when the females interacted with males, their aggressive behavior decreased. The researchers then allowed the female fish to interact socially with a group of other female fish, who had not been exposed to testosterone. It was found that when the female fish stopped receiving testosterone, those who were exposed to the female fish still exhibited the male typical behaviors. In contrast, the female fish who were kept isolated did not continue to exhibit the male typical behaviors after testosterone was discontinued.

Another study exposed male Siamese fighting fish to endocrine-disrupting chemicals. The researchers were curious if exposure to these chemicals would affect the ways in which females respond to the exposed males. It was found that when shown videos of the exposed males, the females favored those who were not exposed to the endocrine-disrupting chemicals, and avoided those male who were exposed. Therefore, the researchers concluded that exposure to these chemicals can negatively affect the mating success of male Siamese fighting fish.

The last study investigated the effect of the SSRI, fluoxetine, on male Siamese fighting fish. It has been previously found that this chemical reduces aggressive behavior; therefore, researchers were curious if this would occur in their experiment. As predicted, it was found that when exposed to fluoxetine, male Siamese fighting fish exhibited less aggressive behavior than they would have if they had not been exposed to the chemical.