Betta Fish (Betta splendens), also known as Siamese fighting fish, betta fish, or Siamese fighters, are highly valued pets by aquarium owners due to the beauty of their fins and colors. One of the main limitations for Betta fish owners is the lack of scientific information on the appropriate conditions to maintain these ornamental fish.
Aquarium fish breeding enthusiasts frequently rely on manuals that are not based on science, their own experience, or advice from friends.
In this article, we aim to provide you with scientifically validated information for the breeding, reproduction, feeding, and care of your Betta fish. At the end of the article, you can find a series of documents where you can delve into certain topics.
Biological Characteristics of Betta Fish
Taxonomy of the Betta Fish
- Domain: Eukaryota
- Kingdom: Animalia
- Phylum: Chordata
- Class: Actinopterygii
- Order: Anabantiformes
- Family: Osphronemidae
- Genus: Betta
- Species: Betta splendens
- English Names: Betta fish, Siamese fighting fish, labyrinth fish.
Anatomical Characteristics
Betta fish are small fish that can live from 3 to 5 years. Males usually reach up to 2 inches long, and females up to 1.5 inches long. They are known for their long, flowing fins, which are especially prominent in males. Betta fish come in a wide variety of colors, including red, blue, green, purple, and white. They can also have patterns, such as stripes, spots, or marbling.
Male Betta Fish
Male bettas are usually more ornate and beautiful compared to females. At two months old, males can be distinguished from females. In nature, male bettas never develop the beautiful fins commonly seen in pet store fish.
Unlike female Betta fish, male Betta fish cannot live together in the same tank. Males will fight to the death, so they should never be placed together in an aquarium. Male bettas are aggressive, flaring their gills and biting the fins of other males. In nature, Betta fish fights can last only 15 minutes.
Female Betta Fish
Female Betta fish have less bright colors than males. Specialists recommend that female Betta fish should not be kept together with males unless breeding is desired.
Although female bettas can fight among themselves when in a small aquarium, fights are very rare.
Habitat
Betta fish (Betta splendens) belong to the family of Labyrinth fish and live in shallow, almost stagnant waters, such as marshes, floodplains, and rice paddies. These fish are native to Southeast Asia, mainly Thailand and Cambodia.
They were first bred for fighting in Thailand around 1850, and their aggressive nature is still evident in today’s males. However, Betta fish have also been selectively bred for their appearance, and now there are many different varieties available in a wide range of colors and patterns.
How Do Betta Fish Reproduce?
Betta fish reach sexual maturity at about five to six months; if you want fish with desired characteristics, you should know the lineage of both male and female bettas.
For breeding, Monvises et al. (2009) recommend that the pair of Betta fish should be placed in an aquarium with vegetation. The water depth in the tank should not exceed 15 cm. Lichak et al. (2022) report success in breeding Betta fish in 5-liter tanks.
The reproductive behavior of Betta fish is notable because the male blows air bubbles at the surface to build the nest. The male Betta does this for hours until he forms a thick bubble nest. He then chases a female. It is recommended to consider a floating substrate for the male to build the nest.
How Do Betta Fish Mate?
Initially, the male Betta tries to court a female under the nest, displaying his fins and flaring his gills. If she does not respond or cooperate, the male Betta can become violent, biting her tail and fins.
When the female Betta is “convinced” to mate and is ready to accept the male, the two “dance,” circling and nudging each other. The male finally wraps a fin around the female, turns her upside down, and fertilizes the eggs she releases.
After releasing, the female remains suspended upside down, as if in a trance, and releases some fertilized eggs, usually three to seven at a time. The male Betta catches the eggs in his mouth as they sink and covers them with mucus before sticking them to his bubble nest. According to Lichak et al. (2022), the number of fertilized eggs released after each reproductive event is around 252.
The male and female Betta will perform the “dance” dozens of times until they have produced hundreds of eggs. When finished, the male aggressively drives the female Betta away and guards the bubble nest until the eggs hatch, which takes 24 to 48 hours. An interesting fact described by Clotfelter et al. (2007) is that female Betta fish prefer to mate with red Betta males compared to blue Betta males; however, the researchers describe that blue male Betta fish are more resistant to diseases.
Caring for Betta Fish Larvae
The male Betta will protect the fry for an additional three to four days while the larvae finish absorbing their yolk sacs. It is important to note that the bubble nest allows the eggs to develop in environments with high temperatures, low pH, and low oxygen levels. The placement of the eggs at the surface increases oxygen exchange (Watson et al., 2019).
The hatching rate of B. splendens significantly decreases at water hardness levels above 540 ppm, registering only 25% success at 900 ppm compared to 78% in the control.
Masculinization of Betta Fish Larvae
As we described earlier, male and female Betta fish have significant morphological differences, with males being more attractive. This makes the prices of males much higher than those of females.
This situation has fueled the interest in having populations of only male Betta fish through masculinization with hormones or sex reversal using androgenic hormones; however, the use of these hormones is prohibited.
What to Do?
Pattiasina et al. (2021) used a natural honey solution for masculinization tests in Betta fish larvae. They report that 12-hour immersion treatments resulted in 93% male ratios and that the most suitable age is 7 days post-hatching. Meanwhile, Kumkhong et al. (2024) achieved masculinization of an entire population of Betta fish with a 45-day treatment group using 60 and 100 mg kg -1 of 17α-MT.
Feeding Betta Fish
In the wild, Betta fish feed on insects, small crustaceans, mosquito larvae, and other aquatic arthropods.
In captivity, Betta fish should be fed twice a day, in the morning and evening. Fish larvae can be fed with infusoria, Artemia nauplii, and water fleas (Daphnia sp and Moina sp) as natural food.
Larger fish can consume pellets or artificial food; however, these must be specific for Betta and should contain at least 35% protein. On the other hand, Thongprajukaew et al. (2023) report that using cooked chicken egg in the diet of male Betta fish achieves the same results as commercial diets.
For Betta fish intended for breeding, in addition to balanced diets, their diet should include adult Artemia, tubifex, or mosquito larvae to improve the quality of the eggs and larvae.
Sipaúba et al. (2016) achieved the best growth and survival rate (82%) of Betta fish with a mixed diet that includes a base diet with 32% crude protein and live food (rotifers, Lecane sp., and the microalgae Asterionella sp. and Melosira sp.). Meanwhile, Montes de Oca et al. (2024) report an improvement in skin coloration and response to induced injuries when Betta splendens are fed Cladocerans enriched with oyster mushroom powder (Pleurotus ostreatus).
Moreover, carotenoids are important in Betta fish feeding, both for the immune response and scale coloration; for example, red Bettas need carotenoids to maintain their color, while blue Bettas do not (Pleeging and Moons, 2017). Likewise, Mejía et al. (2021) report that using mosquito larvae in the diet of Betta fish improves the growth and coloration of these ornamental fish.
What Do Betta Fish Larvae Eat?
Lichak et al. (2022) provides a detailed description of the rearing and feeding of Betta splendens larvae. Table 1 summarizes the different growth stages, care conditions, and feeding.
Table 01. Feeding and care of Betta fish at different stages of development.
| Fish Age | Care | Feeding |
|---|---|---|
| 0 – 4 days post-hatching (DPH) | Petri dish containing blue E1 in an incubator at 28°C. | None |
| 5 – 14 DPH | Static 2.8 L tanks, filled up to 5 cm high with water. 30 fish/tank | 25 mL of concentrated rotifers, once a day. |
| 15 – 30 DPH | 2.8 L tank in a recirculating system. 30 fish/tank | Artemia 2 to 4 times a day. Approximately 4 mL per tank |
| 31 – 62 DPH | 35 L grow-out tanks. 0.5 to 1.0 fish/L | Artemia 2 to 4 times a day. Approximately 10 mL per tank |
| +63 DPH | Individuals raised in 0.8 to 1.4 L tanks. Tanks enriched with plants. | Artemia once a day. Approximately 0.5 mL per tank. Dry pellets (0.5 – 0.8 mm or 1 mm), once a day. |
Breeding Bettas
Southeast Asia is responsible for the largest volume of cultivated Betta fish traded globally. Breeding is conducted in small containers (3.78 – 18.90 liters).
It is important to note that the Ornamental Aquatic Trade Association (OATA) recommends that an aquarium should contain at least four liters of water to prevent the accumulation of toxic products, but this depends on the species.
Once Betta larvae have absorbed their yolk sac (3 days after hatching), they are removed and transferred to grow-out tanks.
Betta fish can be raised together as a group until they reach 3 to 4 months of age, at which point the males should be separated into individual containers to prevent aggression. Females can continue to be raised in groups.
Care of Male Betta Fish
Males can be commercially raised in small bottles. Male Betta fish are kept in these conditions for 8 to 12 weeks depending on their attributes such as size, fin characteristics, and colors desired by aquarists.
At the retail level, male Bettas are typically kept in small tanks. It is important to note that researchers have determined that male Betta fish grow better in tanks with 150 ml of water compared to those with 300 ml of water; in other words, they adapt better to small aquariums. However, it is important to note that in small volumes of water, the level of dissolved oxygen decreases rapidly.
Types of Betta Fish
A total of 73 classes of Betta fish live in the freshwater environments of Southeast Asia. These fish come from the Mekong and Chao Phraya river basins in Thailand (formerly known as Siam).
Betta fish have brightly colored fins and various types of tails (veil, spade, double, crown, halfmoon). Common colors include red, blue, black, white, and orange. Rarer colors include metallic, copper, and turquoise. Recently, photographer Visarute Angkatavanich published a series of spectacular photos of different types of Betta fish on the National Geographic website.
It is important to note that the variety of Betta fish is due to selective breeding by enthusiasts. The main types of tails are veiltail, crowntail, and halfmoon.
If you are interested in genetics, you might find it interesting that research by Zhang et al. (2022) reports a high-quality genome assembly and genetic sequencing of 727 individuals representing diverse morphologies of Betta fish. This can provide more information for the development of new Betta fish varieties.
Care of Betta Fish
Water Quality for Betta Fish Rearing
Bettas are easy to care for in part because they live in tropical waters, with temperatures ranging from 27 to 31.5°C. If we consider the creation of bubble nests by male bettas as a sign of animal well-being, the water temperature ranges between 24.4 and 27.7°C (Pleeging and Moons, 2017), with the majority of bubble nests being built at 26.6°C.
The quality of water in the tank depends on the care provided by the owner. Research shows that Bettas prefer calm water; the use of filters can be hazardous to the health and well-being of your fish. However, regular water changes are necessary. Additionally, fish prefer environments enriched with plants to reduce abnormal betta behaviors.
The level of dissolved oxygen in the water can be low, averaging 3.8 mg/L. Betta fish can obtain oxygen from both air and water due to a lung-like organ. The pH of the water should be maintained between 6.5 and 8. Water should be changed at least once a week.
Puello et al. (2010) demonstrated that adult and larval bettas can tolerate a salinity of 5 ppm without affecting survival or growth rate. She suggests that maintaining breeding bettas at this salinity routinely will not affect color, feeding activity, or reproduction.
Table 02: Key Water Quality Parameters for Betta Fish Care.
| Water Quality Parameter | Range |
|---|---|
| Water Temperature | 24.4 to 30°C, ideal 28°C |
| pH | 6.5 to 8.0 |
| Dissolved Oxygen | > 3.8 mg/L |
| Tank Volume | 4 liters per fish |
| Water Change | 25% weekly |
| Water Hardness | Up to 20 dGH |
| Ammonia | < 0.25 ppm |
| Photoperiod | 14:10 hours Light:Dark |
Behavior and Compatibility
Betta fish are known for their territorial behavior, especially the males. This means they should not be housed with other male betta fish, as they will fight and can even kill each other. Females are less aggressive but can still be territorial among themselves. Betta fish are also relatively inactive and spend most of their time swimming around their tank or resting on plants or decorations.
You cannot place two male betta fish in the same aquarium; they will fight until one dies. Regarding this, Oliveira et al. (2022) highlights that a dose of oxytocin at 7.5 µg/g reduces aggressive behavior in B. splendens.
On the other hand, in larger tanks, betta fish could coexist with gouramis, neon tetras, and catfish.
Transporting Betta Fish
According to data from wholesalers of ornamental fish in Florida (USA), at least 2% of betta fish die during transport, and less than 0.5% die in retail trade. In this regard, if you need to transport betta fish, you should consider that they must be moved individually in plastic bags with 10 ml of air per fish (a water-to-air volume ratio of 1:3), allowing for journeys of up to 5 days.
Additionally, Thongprajukaew et al. (2023) determined that the minimum volume of water that B. splendens tolerated well during transport was 80 ml, and these results can be used as a guide for local overland shipment of male Siamese fighting fish.
Diseases of Betta Fish
Betta fish are susceptible to several diseases, including:
Velvet Disease
This is a parasitic infection caused by dinoflagellates of the genus Oodinium, which causes white spots to appear on the fish’s body. The easiest way to identify betta fish with velvet disease is by observing a gold dust-like layer on the fish’s body (Lichak et al., 2022).
For the treatment of this disease, Lichak et al. (2022) recommends a 5-day treatment cycle of Proform C (Pentair, Cary, NC) at a dose of 30 μL per liter of tank volume, with daily 100% water changes.
Fin Rot
Fin rot is a bacterial infection that causes fins to fray and rot. Lichak et al. (2022) recommends treating fish suffering from this disease with a 4-day treatment of Furan 2 (nitrofurazone) antibiotic at 46 mg/L, with 100% water changes daily.
Mycobacteriosis
Mycobacteriosis is the most common cause of death in bettas in fish farms in Thailand, and it also poses risks to humans. Sick bettas develop granulomas in the liver, spleen, and kidneys. Other symptoms include anorexia, exophthalmia, keratitis, and skeletal deformities.
There is no definitive treatment for mycobacteriosis; prevention is the best alternative. Dinh-Hung et al. (2024) reported that ozone nanobubbles effectively reduce bacterial concentrations in water, mitigate the risk of mycobacteriosis, and improve the survival capacity of betta fish exposed to multi-drug-resistant Mycobacterium chelonae.
Other Diseases
Betta fish, and freshwater ornamental fish in general, are often parasitized by the dinoflagellate Piscinoodinium or the fungus Saprolegnia. Young bettas are especially sensitive to infection and disease development. Effective treatment includes baths with saltwater up to 5 ppm.
If you notice any signs of illness in your betta fish, it is important to treat the disease as soon as possible. There are several over-the-counter medications available, or you can take your fish to a veterinarian.
Conclusion
The betta fish is an excellent choice for keeping in home aquariums; however, it also requires care and attention. In this regard, you should provide your fish with basic water quality conditions to ensure their well-being.
Furthermore, if you are considering breeding and selling these specimens, we recommend reviewing the bibliography section where you will find more information about betta fish.
References
Betta Fish Homepage. Adelphi University.
Clotfelter E., Daniel R. Ardia, Kevin J. McGraw, Red fish, blue fish: trade-offs between pigmentation and immunity in Betta splendens, Behavioral Ecology, Volume 18, Issue 6, November 2007, Pages 1139–1145, https://doi.org/10.1093/beheco/arm090
Dinh-Hung, N., Dong, H. T., Senapin, S., Shinn, A. P., Linh, N. V., Dien, L. T., Soontara, C., Hirono, I., Chatchaiphan, S., & Rodkhum, C. (2024). Using ozone nanobubbles to mitigate the risk of mycobacteriosis in Siamese fighting fish (Betta splendens). Aquaculture, 581, 740390. https://doi.org/10.1016/j.aquaculture.2023.740390
Krishnakumar, A., Patrick Anton, E.S. & Jayawardena, U.A. Water hardness influenced variations in reproductive potential of two freshwater fish species; Poecilia reticulata and Betta splendens. BMC Res Notes 13, 542 (2020). https://doi.org/10.1186/s13104-020-05382-x
Kumkhong, S., Chukerd, N., & Phumrojanar, P. (2024). The optimum dose and period of synthetic hormones 17-α methyltestosterone during fry stage on masculinization of Siamese fighting fish (Betta splendens). Food Agricultural Sciences and Technology, 10(1), 17-28.
Lichak, M. R., Barber, J. R., Kwon, Y. M., Francis, K. X., & Bendesky, A. (2022). Care and use of Siamese fighting fish (Betta Splendens) for Research. Comparative medicine, 72(3), 169-180.
Mejia-Mejia M., Elsah Arce, Judith García-Rodríguez, Luis M. Burciaga. 2021. Effect of feeding mosquito larvae on the coloration of Siamese fighting fish (Betta splendens) during grow-out. Int Aquat Res (2021) 13:71–79 https://doi.org/10.22034/IAR.2021.1916191.1116
Monvises A., Bunlung Nuangsaeng, Namkang Sriwattanarothai, Bhinyo Panijpan. 2009. The Siamese fighting fish: Well-known generally but little-known scientifically. Science Asia 35: 8-16.
Montes de Oca, S., Téllez-Téllez, M., Arce, E., García-Rodríguez, J., Burciaga, L. M., & de Lourdes Acosta-Urdapilleta, Ma. (2024). Effect of mushroom powder (Pleurotus ostreatus and Pleurotus djamor) on skin coloration and inflammation in siamese fighting fish (Betta splendens). Journal of Applied Aquaculture, 1–16. https://doi.org/10.1080/10454438.2024.2351376
Oliveira, J. A., da Silva Souza, J. G., de Jesus Paula, D. A., Virote, B. D. C. R., & Murgas, L. D. S. (2022). Oxytocin reduces the frequency of aggressive behaviours in male betta fish (Betta splendens). Behavioural Processes, 200, 104689.
Pattiasina B. J., M. Pattinasarany, M. Manuputty and E. Kokmesa. 2021. Masculinization of beta fish larvae Betta splendens through the different treatment immersion of honey solution and larval age. IOP Conf. Ser.: Earth Environ. Sci. 797 012016
Pleeging C. and C. Moons. 2017. Potential welfare issues of the Siamese fighting fish (Betta splendens) at the retailer and in the hobbyist aquarium. Vlaams Diergeneeskundig Tijdschrift, 86.
Puello A., G. Velasco, I. Martínez, E. Felix, D. Voltolina. 2010. Growth and Survival Fighting Fish, Betta splendens, Larvae at Low Salinity and With Different Diets. Journal of the World Aquaculture Society, Vol. 41, No 5.
Saekhowa, S., Nuntapongb, N., Rungruangsak-Torrissenc, K., & Thongprajukaewa, K. (2022). Efficiency of homemade egg-based diet for male Siamese fighting fish (Betta splendens). Energy (kcal/kg), 4796(3150), 3476.
Sipaúba L., A. Apploni, J. Fernandes and R. Millan. 2016. Feed of Siamese fighting fish, Betta splendens, (Regan, 1910) in open pond: live and formulated diets. Braz. J. Biol., 2016, vol. 76, no. 2, pp. 292-299.
Thongprajukaew, K., Takaeh, S., Esor, N., Saekhow, S., Malawa, S., Nuntapong, N., … & Choodum, A. (2023). Optimal water volume for transportation of male Siamese fighting fish (Betta splendens). Aquaculture Reports, 28, 101430.
Watson C., Matthew DiMaggio, Jeffrey Hill, Quenton Tuckett, and Roy Yanong. 2019. Evolution, Culture, and Care for Betta splendens. Institute of Food and Agricultural Sciences (IFAS) – University of Florida. 5 p.
Zhang Wanchang, Hongru Wang, Débora Y. C. Brandt, Beijuan Hu, Junqing Sheng, Mengnan Wang, Haijiang Luo, Shujie Guo, Bin Sheng, Qi Zeng, Kou Peng, Daxian Zhao, Shaoqing Jian, Di Wu, Junhua Wang, Joep H. M. van Esch, Wentian Shi, Jun Ren, Rasmus Nielsen, Yijiang Hong. 2022. The genetic architecture of phenotypic diversity in the betta fish (Betta splendens). Science Advances 2022-09-23 8(38); doi: https://doi.org/10.1101/2021.05.10.443352
