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Betta Fish (Betta Splendens) Caresheet


The name “Betta” for this popular fish stems from the genus to which it belongs. It is classified as an anabantoid, or labyrinth fish, and is related to gouramis and climbing perch.

In the aquarium trade, the Betta fish commonly encountered at pet stores is primarily the species Betta splendens. However, some are hybrids of a few species in the Betta genus, including B. imbellis, B. smaragdina, and B. mahachaiensis.  The care requirements do not differ between hybrids and true B. splendens.

The Betta fish is also known as the Siamese Fighting Fish because where it originated (Thailand, Cambodia, Vietnam, Malaysia) it was often used for sport. The fish are naturally aggressive towards conspecifics, and when placed in small containers together, would fight to the death. Thankfully, they were selectively bred for their beauty over the years and “fighting” them has fallen out of favor.


Betta fish come in almost every color imaginable. The wild type fish is a brownish color with blue and red accents, but they have been selectively bred for over a hundred years to the point where you can now get them in purple, orange, white, yellow, marbled, you name it! Some fish have an added iridescence known as “dragonscale.” They also come in a variety of fin types. Some have long, veil tails, while others have the traditional short fins that their wild ancestors possessed. There are also crowntails, doubletails, half moon, and delta. There are even some that have enhanced pectoral fins, also known as “dumbos.”


Although long touted as a fish that thrives in bowls and other tiny containers, we do not recommend any aquarium smaller than five gallons to house one betta. You can read more about why bowls and other unheated/unfiltered containers are problematic in Beware of Bowls. Despite the fact that bettas are slow moving and breathe atmospheric air (thanks to that labyrinth organ, hence “labyrinth fish”), they still hugely benefit from filtered, oxygenated water and a little room to move around. Males of this species must be housed separately to avoid fighting. Females can be housed together in spacious aquariums (20 gallons or more). A single male or multiple females can also be housed with other peaceful species of fish in a larger community type setting. Because of the need to breathe atmospheric air, there should be room between the surface of the water and the lid of the aquarium for bettas to take a quick breath. Care should be taken to adequately cover all openings in the aquarium, because these fish have a tendency to jump. 



While bettas can survive at room temperatures, they are much more lively and healthy at 76-82 degrees fahrenheit. This temperature is best achieved with a heater. The adjustable heaters tend to be a little safer because you can dial them in, but there are plenty of reliable preset heaters on the market as well. Another reason we recommend at least five gallons per betta is because a preset heater stuck on is less likely to cook this volume as quickly as, say, a quarter gallon bowl. You will want a thermometer regardless to monitor daily temperatures and to keep tabs on whether or not your heater is working properly. 


Fancy bettas are adaptable from a pH of 6 all the way up to 8. They can tolerate a correspondingly high degree of hardness as well; however, they may not breed unless you lower this. Betta fish coming directly from the wild are a little pickier than the selectively bred varieties on the market today, preferring a more acidic pH and appreciating lots of leaf litter. However, unless you are working with these wild caught animals, you usually do not have to fiddle with pH much. As long as you are not using water with a pH of 9 and a hardness of 20+ degrees (KH/GH), or the other extreme of distilled or RO water with no minerals, you usually do not need to fuss over pH. As long as your betta is carefully acclimated to your water, they should adapt quickly and lead long, happy lives.


Betta aquarium maintenance will be similar to any other aquarium maintenance. Once established (or “cycled”), your aquarium should receive a partial water change of  25% once a week. In emergencies, up to 50% of the water can be replaced. Water changes are best done with a gravel siphon to pull any hidden debris out of the substrate. Whenever water is changed, make sure it is a similar temperature and to treat it with a dechlorinator if you are using tap water. Chemical filter media (such as carbon) can be replaced monthly. Any biological media (sponges, ceramic media, etc) should be touched only sparingly and replaced when it degrades, which can take years. If rinsing any of the biological media/sponges, do so only in treated water as any chlorine or chloramines will kill the beneficial bacteria that lives on it.


Males of this species must be housed separately to avoid fighting, as they will not tolerate each other. Males and females also should not be housed together. Females, however can be kept together in spacious aquariums (20 gallons or more).A single male or multiple females can also be housed with other peaceful species of fish in a larger community type setting. They should not be housed with boisterous or nippy fishes such as large barbs or cichlids.


Betta fish typically get anywhere from 2-3 inches in total length as adults. The exception to this are the giant varieties, which can get over 5 inches!


Bettas are carnivorous, primarily eating insects and insect larvae in the wild. They will appreciate offerings of live foods such as blackworms, white worms, and daphnia and frozen bloodworms and brine shrimp. However, they will do just fine on a pellet diet targeted specifically for bettas. It recommended to offer a pellet as the staple diet and mix things up with live, frozen, or dried treats from time to time.


Betta splendens are sexually dimorphic in the sense that in most fancy varieties, the male will have long flowing fins and females will have short, rounded fins. However, in short fin varieties this will not be the case. Generally speaking, a mature female will be distinguishable by a white ovipositor (egg tube) sticking out of the vent and a fuller abdomen. Mature males will have a more broad head, have a more slim abdomen and no ovipositor. Males also tend to flare their fins and operculum (gill cover/gills) when they feel threatened, whereas females are less inclined to do this. 


Breeding bettas is a bit of an art form, especially for the bubble nesting species such as Betta splendens. Both male and female fish must be well conditioned and receptive for it to work. They will require a separate breeding tank, usually 10 gallons is acceptable. The aquarium should be about half full, and the pH should be lowered with the addition of leaf litter or blackwater extract. Bettas will not breed unless the water is at least 80 degrees fahrenheit, so be sure to include a small heater. This aquarium should not have any vigorous water movement. A tiny sponge filter in the corner of the aquarium on low flow can be utilized, as long as there is a calm area for the male to build his bubble nest. You will also want a tight lid to keep the humidity and warmth above the water level high. This will be crucial for maintaining the nest and for raising the fry.

The male should be alone in this aquarium to begin with for a couple days to get accustomed to his surroundings. You should condition the female in a separate aquarium. When both fish look ready, take a clear container and place it in the male’s aquarium such that he can see it but not access it. Place the female in this container and let the fish view each other. Give the male a day or two to build his nest (a concoction of saliva and air which will host the eggs/fry). If the fish seem receptive, you may gently introduce the female into the aquarium with the male.

Watch them carefully. If they are ready, the male will start to flare and attract the female to his nest. If she does not follow him and is instead chased and harassed, you will want to remove the female. The male will eventually kill her if she does not reciprocate. If the female does reciprocate, the male will embrace her under the nest, wrapping his body around her completely. There will be a brief squeeze and then sperm and eggs will be released. The fish will be temporarily paralyzed, with the male typically coming around before the female. He will hunt down all of the eggs and spit them into his nest before the female has a chance to eat them. They will repeat these embraces until the female is spent of eggs, at which point you will want to remove her from the aquarium.

The male assumes parental care of eggs and will tend to his nest until they hatch, usually three days later. Once the fry are free swimming, you will want to remove the male and raise them in the breeding aquarium. You can expect 40-50 fry per spawn on average. They will require microscopic foods to survive, such as infusoria, paramecium, vinegar eels, or golden pearls.