Siamese Fighting Fish
- 演化之聲
- Mar 16
- 6 min read
The Siamese fighting fish (Betta splendens), commonly known as the Siamese fighting fish or betta, is a freshwater species native to Southeast Asia. Its natural distribution includes Thailand, Cambodia, Laos, Vietnam, Malaysia, and Myanmar. In the wild, these fish are most often found in rice paddies, marshes, shallow ponds, and densely vegetated wetlands. Because these habitats are typically shallow and easily become oxygen-poor under high temperatures, the species has evolved the ability to breathe atmospheric air directly at the water surface. This adaptation allows them to survive in conditions that would be difficult for many other fish.
Wild individuals generally do not possess the striking colors seen in selectively bred ornamental strains. Their natural coloration tends to be brownish or greenish-gray, and their fins are relatively short. Brighter coloration usually appears only when the fish are threatened or during courtship displays. Male bettas are naturally aggressive and territorial. They challenge rivals by spreading their fins, expanding their opercula, and adopting threatening postures, sometimes leading to brief combat. Females are typically less aggressive toward one another, although limited space can still result in occasional conflict.
The domestication of Siamese fighting fish has a history spanning several centuries, originating in the central plains of Thailand. Early breeders selected individuals with stronger aggressive tendencies for use in organized fish fights and gambling competitions, a tradition that persisted in the region for a long time. During the nineteenth century, the King of Siam presented some specimens to Western scholars, allowing the species to gradually spread to Europe and North America. By the early twentieth century, it had become a popular ornamental aquarium fish. After centuries of selective breeding, modern bettas now exist in numerous strains, displaying an extraordinary diversity of colors and fin shapes, including solid colors, bicolor patterns, marble patterns, and distinctive fin types such as halfmoon, double tail, and crowntail forms.
Although the species is abundant in captivity, wild populations have declined due to habitat destruction and water pollution. As a result, the International Union for Conservation of Nature (IUCN) has classified the species as Vulnerable. Expansion of rice cultivation, the spread of palm plantations, and contamination from agricultural chemicals have gradually reduced the natural habitats where these fish once thrived. This contrast between global popularity in aquariums and the decline of wild populations underscores the importance of conserving natural habitats.
Housing Requirements in Captivity
In home aquaria, Siamese fighting fish are often mistakenly believed to tolerate very small containers such as cups or glass jars. However, if long-term health and longevity are desired, an appropriate aquarium environment should be provided. A tank with a capacity of at least 20 liters is generally recommended. The aquarium should also have a lid, as bettas are capable jumpers and may leap out of uncovered tanks. Water temperature should ideally be maintained between 24 and 28°C. Temperatures that are too low can weaken the immune system and increase susceptibility to disease, while excessively high temperatures may accelerate metabolism and induce stress.
Regarding water chemistry, bettas can tolerate mild variation in acidity and alkalinity, but neutral to slightly alkaline conditions (pH around 7.0 to 7.5) are generally suitable. Because they can breathe air at the water surface, they are less dependent on highly oxygenated water than many other tropical fish. Nevertheless, this does not eliminate the need for proper water quality management. Prolonged exposure to turbid water or high ammonia levels may lead to fin rot or bacterial infections. Installing a small filtration system and performing regular partial water changes is therefore recommended.
Aquarium decoration and habitat structure are important for the psychological well-being of these fish. Bettas tend to establish territories among plants, stones, and branches, so the tank should contain sufficient aquatic plants or artificial vegetation. Floating plants are particularly useful because they replicate the shaded conditions found in rice fields or ponds, providing suitable locations for males to construct bubble nests and giving the fish a sense of security. Decorative objects should not have sharp edges that could damage their delicate fins. Indian almond leaves (from Terminalia catappa) are commonly used by aquarists; they release tannins that may help suppress microbial growth, stabilize water chemistry, and recreate a habitat atmosphere closer to natural conditions.
Male bettas possess strong territorial instincts and should generally not be housed together in the same tank. However, in sufficiently large aquaria with adequate hiding spaces, they may sometimes coexist with small, peaceful schooling fish such as neon tetras (Paracheirodon) or zebrafish (Danio rerio). Species with long flowing fins or bright coloration, as well as goldfish, should be avoided because they may provoke aggressive attacks. Females are typically less territorial and can occasionally be maintained in groups under carefully monitored conditions, although social interactions should still be observed to prevent stress or injury.
Feeding Conditions
In the wild, Siamese fighting fish are carnivorous. Their diet mainly consists of small aquatic crustaceans, insect larvae, and zooplankton, and they may also consume flying insects that fall onto the water surface. In captivity, a diet rich in protein is recommended. Suitable foods include specially formulated betta pellets as well as live foods such as bloodworms, water fleas (Daphnia), and brine shrimp. Dry flake foods are generally less accepted, and some individuals may refuse them entirely.
Feeding should follow a principle of moderate portion size and regular frequency. Feeding twice per day is typically sufficient, with each feeding limited to an amount that can be consumed within about five minutes. Excess food can quickly degrade water quality and may also cause digestive problems such as constipation or abdominal swelling. Live foods should be obtained from reliable sources to minimize the risk of introducing parasites or pathogens. Juvenile fish require very small live foods during early development, such as rotifers or newly hatched brine shrimp, gradually transitioning to larger foods as they grow.
To maintain vitality and proper nutrition, it is advisable to vary the diet rather than relying on a single food source. Some aquarists also introduce occasional fasting days within the feeding schedule. These brief fasting periods may allow the digestive system to rest and reduce the risk of gastrointestinal disorders.
Breeding Conditions
The breeding behavior of Siamese fighting fish is distinctive. During courtship, the male first constructs a bubble nest at the water surface. Using mucus secreted from the mouth, he stabilizes clusters of air bubbles to form a floating foam structure. When the male displays and spreads his fins to attract a female, a receptive female will darken in coloration and develop vertical body stripes, indicating readiness to spawn. The male then wraps his body around the female in a behavior often called the “embrace,” stimulating egg release. Each spawning event may produce dozens of eggs. The male simultaneously releases sperm into the water to achieve external fertilization, then carefully collects the fertilized eggs in his mouth and places them one by one into the bubble nest.
Throughout the reproductive process, the male performs all parental duties. After spawning, the female is typically chased away by the male and should be removed from the breeding tank immediately to prevent injury or death from repeated attacks. The male continuously repairs the bubble nest and retrieves any eggs that fall, returning them to the nest until hatching occurs. Eggs usually hatch within about 24 to 36 hours. The larvae initially survive on their yolk sacs and begin free swimming after approximately two to three days. At this stage the fry are extremely small, and suitable microscopic live foods must be provided.
Breeding should be approached with careful planning. Newly hatched fry require well-maintained water quality and precise feeding management in order to develop successfully. Because a single spawning event may produce more than one hundred offspring, aquarists should consider in advance whether sufficient space and resources are available to raise or distribute the young fish, preventing overproduction and potential abandonment.
Preventing Invasive Spread
Because of their ornamental appeal, Siamese fighting fish are widely kept around the world, and wild populations have already been recorded in many regions outside their native range. Established populations have been documented in places such as Florida and Texas in the United States, the Northern Territory of Australia, and Singapore. These populations often originate from irresponsible release by aquarium owners or accidental escape. Once established in local waterways, they may compete with native fish, amphibians, or aquatic insects, potentially causing ecological disruption. In the Adelaide River floodplain of Australia, introduced betta populations have already been regarded as invasive fish threatening native wetland species.
Aquarists therefore have a responsibility to follow the principle of not releasing captive animals into the wild. If personal circumstances prevent continued care of the fish, alternative solutions should be sought, such as transferring them to other hobbyists or consulting local aquarium stores about possible rehoming. These actions help prevent ecological damage that could otherwise be difficult or impossible to reverse.
Author: Shui-Ye You
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