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How should I care for my Siamese fighting fish?

aquarium betta

Siamese fighting fish (Betta splendens) are a very popular aquarium fish. They originate from tropical regions of Southeast Asia and, today, there are a wide variety of Siamese fighting fish types and colours available.

Purchasing a healthy Siamese fighting fish

When purchasing a Siamese fighting fish first check that the seller is reputable and that their aquariums are not overcrowded. Purchasing from a large aquarium store will generally be a good option. Healthy fish display clear and bright body colouration, and they hold their fins erect. Healthy fish are also alert and swim without undue effort.

Indicators of poor health include fish that sink or bob to the surface; fish that have lumps, bumps, wounds, clamped fins, or a trail of excreta (faeces) and fish that stay in a corner of the aquarium for a prolonged period of time.

Tank size

Tanks for housing Siamese fighting fish ideally should be 20 litres or more in volume to allow your fish to display normal activity, with 10 litres being the absolute minimum ​[1]​. Small tanks or fish bowls do not provide adequate space to meet the fish’s physical and mental needs.

Siamese fighting fish are excellent jumpers, so the tank should be fitted with a lid to prevent escape. Siamese fighting fish require occasional surface air, even if water oxygen is plentiful, so there must be some space between the water and the tank lid in which to take in air.

Regardless of the shape, all tanks should have a covered area/side where the fish are not exposed to bare glass. This promotes better welfare for your Siamese fighting fish, as they will be less stressed and feel more secure.

Heater and thermometer

Siamese fighting fish are from a tropical climate, so heating is essential. The tank should be heated using a submersible aquarium heater and the temperature maintained between 24 to 26 ℃. Normal room temperature is not suitable as is generally too cold, and can also fluctuate, which can be stressful to the fish.

Small fish bowls are usually too small to fit a suitable heater and thus cannot properly regulate and maintain a constant temperature. Some bowls/tanks are sold with small lamps above them, suggesting that this will provide adequate heat. However, these lamps are usually switched off at night and the heat provided may be either insufficient or excessive depending on the surrounding area/climate the bowl is kept in. A submersible aquarium heater is the only way to achieve and maintain a constant and appropriate temperature for Siamese fighting fish.

Water quality

Good water quality is essential for any aquarium and is the key to helping your Siamese fighting fish remain healthy. Regularly test your water for ammonia, nitrite, and nitrate levels to ensure your biological filtration is working, you are maintaining it appropriately and your aquarium is not overstocked or over fed.

Refer to article Why is water quality important when setting up a fish aquarium?

Other water parameters to monitor include pH and water temperature.

Ideal water parameters for Siamese fighting fish are:

  • Ammonia < 0.1 ppm
  • Nitrite < 0.2 ppm
  • Nitrate < 50 ppm
  • pH 6.5 to 7.5
  • Temperature 24 to 26°C

When starting a new aquarium, until the Nitrogen Cycle is established, test the water every two to three days for ammonia and nitrite for the first six weeks. After this testing every one to two weeks is sufficient.

Further information and videos are available at Aquarium Care 101 (Aquarium School / The Aquarium Vet).

Filtration and aeration

Siamese fighting fish require efficient filtration of a suitable size to maintain water quality and for aeration. Good filtration will ensure all water is regularly filtered mechanically and biologically via the nitrifying bacteria in the filter media which convert the toxic ammonia released from decaying fish waste into less harmful nitrates. If the filter does not create bubbles or stir the surface water, aeration with an air stone is needed to ensure that the water is well oxygenated.

A filter of appropriate size for the tank with adjustable flow is needed. Siamese fighting fish prefer low flow as this mimics their natural habitat.

Tank maintenance

Weekly partial water changes of 10 to 25% of the tank water are recommended combined with a gravel clean to remove waste and to help your Siamese fighting fish remain healthy.

A gravel siphon purchased from a pet store should be used. Gently shake the siphon briefly in the aquarium to start the flow of water into a bucket below. Use a dedicated (labelled) fish bucket which will not be used for other purposes to avoid any harmful chemical residues. The end of the siphon in the tank can be used to clean the gravel by vacuuming the substrate to remove fish faeces and any uneaten food. Fish can stay in the aquarium while siphoning to minimise stress, though care should be taken not to move too rapidly as this may stress the fish.

NEVER suck on the hose to start a siphon as this can cause human health issues.

After 10 to 25% of the water is drained, replace the water with cold tap water. It is worth having a second bucket that was filled the day before with tap water. This allows some of the chlorine to gas off and. also brings the water temperature up to room temperature. Before adding any new water, it is very important to add the appropriate quantity of an aquarium Water Conditioner (sometimes called water agers) to neutralise the chlorine and chloramine present in the tap water. Carefully read the label of the product that you are using.

Handy Tip – use the old aquarium water on your plants. It is a great fertilizer.

The filter should be rinsed lightly in a bucket of tank water when it starts to get clogged up or on a monthly basis (whichever occurs first). It is important to avoid over-cleaning the filter media as this will remove the beneficial bacteria. Without beneficial bacteria in the filter, ammonia from fish waste will not be broken down to less harmful nitrates, leading to fish death. Do not use tap water to clean the filter, as the chlorine (or chloramines) may also kill the beneficial bacteria.

The inside of aquariums can be cleaned of any algae build-up by wiping the insides gently with a clean, aquarium safe sponge or with a magnetic glass cleaner. Never use soap or detergents when cleaning an aquarium.

Periodically altering the direction of water flow in your aquarium, will also provide some environmental enrichment for your Siamese fighting fish.

Behaviour and environmental enrichment

It is normal for some Siamese fighting fish to ‘hang out’ or rest in one area or for a while, with some fish being more active than others. A healthy fish is always responsive, moderately active, and inquisitive. Any fish which is constantly hiding or appearing lethargic and unresponsive to its owners is likely to be stressed or suffering illness and should be provided with appropriate veterinary care.

Male Siamese fighting fish will sometimes construct bubble nests as a sign they are ready to breed. These appear as a cluster of small bubbles of various sizes on the surface of the tank in a corner or area where there is some cover. This is normal behaviour.

Siamese fighting fish originate from densely vegetated areas and tend to prefer a tank with several plants (real or artificial), and/or other forms of cover in which to explore, rest, and hide. This will provide a stimulating environment for your fish and reduce stress. Siamese fighting fish will be more active, inquisitive, and interesting to watch when they feel secure in their environment. Only source live plants from an aquarium store. Do not collect from the wild as you may introduce parasites or disease into your aquarium. Also only use plastic plants purchased from an aquarium store.

To ensure fins are not torn, gravel should be smooth and decorations such as silk or live plants should not have rough edges. Male fish with long fins are particularly prone to fin tears. Sharp edges and points on some decor and driftwood can be sanded gently to make it safe.

As Siamese fighting fish require surface air supplementation to survive, being close to the surface is beneficial when resting. Providing tall plants with large leaves on which fish can rest at night can assist with this.

Mirrors should never be used in a tank as these lead to male Siamese fighting fish constantly ‘flaring’ their fins because they see another male fish and become aggressive. This constant ‘flaring’ of fins can cause stress and exhaustion.


Overfeeding of Siamese fighting fish is common, leading to obesity and other health issues. Uneaten food also breaks down and contaminates your aquarium. Feed your Siamese fighting fish once a day and only what can be eaten in under two minutes. A varied diet will maximise the health of your Siamese fighting fish.

You should offer high quality specialised Siamese fighting fish pellets/granules and occasionally supplement this with frozen black worms, brine shrimp, frozen tubifex worms and daphnia, which will offer a varied diet and provide some enrichment.

Mammalian fats (e.g. from beef heart, meat, offal) are poorly digested in fish, and should not be fed to Siamese fighting fish.


To minimise algae outbreaks, aquariums should ideally be kept away from direct sunlight or windows. Aquarium lights should be left on for a maximum of 10 hours a day.

It is also important that your Siamese fighting fish have a minimum of eight hours of darkness, so make sure all lights or lamps are turned off at night in the area that your aquarium is located.

Can I house other fish with my Siamese fighting fish?

Two male Siamese fighting fish will fight to protect their territory and should never be placed in the same tank. One will end up dying. Females will often be more peaceful together and with other peaceful fish species, however, they also have the potential to be aggressive on occasion.

Male and female Siamese fighting fish should only be housed together for the purpose of breeding. They are likely to become aggressive with each other either before or after breeding. Breeding Siamese fighting fish requires a lot of time, experience, and resources as many tanks are needed for the fry (who will eventually fight).

Attempting to house male Siamese fighting fish with other types of fish is not recommended for beginner fish carers, though aquatic snails or large shrimps (note that smaller shrimps may be eaten) can be suitable companions. If a community tank is desired, Siamese fighting fish can sometimes be kept with smaller peaceful fish such as corydora, otocinclus catfish, and/or neon tetras. Tetras are best kept in a shoal of five or more of the same species. Other tetras such as widow, serape, and cochus blue tetras are not recommended as they can nip fins. You will need a tank with a capacity of at least 40 litres for one Siamese fighting fish and a shoal of small community fish, with an extra 20 litres recommended for a large shoal or each additional small shoal of another species. Increased plant cover is also advised to reduce stress by providing separate territories and hiding places. Community fish which swim at different levels in the aquarium to the Siamese fighting fish (such as the mid to lower tank levels) are preferred as Siamese fighting fish often claim the upper sections of the tank.

A backup tank should be available in case the Siamese fighting fish becomes aggressive or the additional fish begin to nip or harass the Siamese fighting fish, which can often occur with male fish that possess long finnage.

Emergency preparedness

Unfortunately, there is always the possibility that you will need to move or transport your fish in an emergency. This may be because the tank develops a leak or a more serious emergency such as fire or flood. Being prepared for such an emergency is important as transporting your fish safely requires specific equipment and preparation and the survival of your fish can depend on this. For information on preparing an emergency fish transport plan and kit, see this article.

For more information, it is recommended that you talk to an experienced aquarist (fish carer) or fish veterinarian.

AUTHOR – Dr Rob Jones (The Aquarium Vet)


​​[1] Oldfield RG, Murphy EK (2024) Life in a fishbowl: Space and environmental enrichment affect behaviour of Betta splendens. Animal Welfare 33:e1

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Updated on May 1, 2024
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