Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish

Betta Splendens

Siamese fighter, Betta splendens
Siamese fighter, Betta splendens


Betta splendens or as it is better known the Siamese Fighter is a member of the Order Perciformes (Perch like fish) but it has been moved from the Labyrinth family (Anabantidae) to the Gourami family (Osphronemidae). They are rightly very popular due to their ornate finnage and bright colours which making them one of the most beautiful of all fresh water fish. Their other call to fame is due to the males complete intolerance of other males. Male Bettas will fight on site of each other and where these fish occur in the wild organised contests take place with large bets placed on the outcome.

The males intolerance is based on being very territorial, the males defend a small area where they prepare a nest of bubbles ready to attract a mate. The nest area will be defended from all other males and even from females who are unable or unwilling to spawn, both will be forcefully driven away.


Before moving on to their captive care it is important to look at where Betta splendens comes from and how it lives in the wild. Betta splendens comes from the Mekong basin in Asia. They occur in rice paddies, flooded plains, canals and in the bank vegetation of both large and small slow moving rivers and always in shallow water. They live in dense vegetation where they move amongst the leaf litter looking for their prey.

The water conditions found in the wild do vary but almost always within the following range.

  • Temp - 24° to 30°C, (75° to 86°F)
  • pH - 6 to 8
  • GH - 5 to 19

Due to rotting vegetation the water can be quite low in oxygen. To cope with this Betta splendens has a labyrinth organ which allows the fish to breathe oxygen directly from the air. This organ has become so important to the Betta that if they are prevented from coming to the surface for a breath they will actually drown.


Wild Betta splendens feed almost exclusively on aquatic insects and airborne insects which have become trapped on the water surface, they eat little or no vegetation.

Live or frozen food such as bloodworms, daphnia, mosquito larvae, small earthworms, high quality flake food and freeze dried food all have a place in a Betta's healthy and varied diet. Due to the high protein nature of the diet the fish should be fed no more than once or twice per day.

Captive care


As previously mentioned Betta splendens inhabits still shallow water, in the tropics such water becomes quite warm and Betta splendens has evolved in those conditions. Betta splendens needs to be kept warm, cool or fluctuating temperatures will eventually have an impact on the health of the fish.

I have heard an argument which says that at cooler temps their metabolism is slowed down and that they will live longer as a result. Unfortunately this is only half true, their metabolism will be slowed and as a result their ability to digest food will be impaired which in turn means the food will be in there for longer, increasing the risk of a blockage. The fishes immune system will also work less efficiently which could allow an opportunistic infection which would normally be quite benign to take hold. Healing will take longer leaving the fish more exposed to infection. Fish with very long fins may not heal at all at the extremities of the fins leaving the fish looking quite tatty.

Betta splendens is a normally active fish which is interested in its surroundings, at low temperatures it will become lethargic and disinterested. Heaters don't cost very much so there is no real excuse for not using one,

Betta splendens is a tropical fish and should be maintained at a minimum and steady temp of 24°C (75°F).

Water Quality

Due to rotting vegetation the water can become quite low in oxygen, Betta splendens can easily cope with this but unfortunately for them they can also cope with reduced water quality for a short time and this has lead to abuse. Although Betta's can cope with reduced oxygen levels they are still susceptible to ammonia and nitrite poisoning in the long term. Nitrite poisoning even from very low levels of nitrite will reduce the fish's bloods ability to carry oxygen because the nitrite binds to the haemoglobin preventing it from carrying oxygen. Because Bettas can breathe air which has many times the amount of oxygen that water has the symptoms remain hidden for a much longer period than would be the case with most other fish. Bettas do not have the ability to cope with either nitrite or ammonia, they can only cope with reduced oxygen levels.

Ammonia is excreted from the fish's gills especially after feeding and more so when the diet is high in protein like that of the Betta. Ammonia will appear in the water within an hour of feeding the fish so even a twice weekly water change of any size will still mean that the fish spends much of its life being exposed to a deadly toxin. The only satisfactory way to deal with ammonia and nitrite is to remove it, this is very easily accomplished with a small biological filter i.e. a small air powered sponge filter.


This is an area open to debate. Bettas in the wild hold small territories of about 60cm (2ft)  in diameter which roughly equates to about 100 litres (depending on the depth of water). but this needn't be the case in captivity. A more important concern is maintaining a healthy living environment so the tank must be able to accommodate both a heater and a small filter. Because of this I would recommend a minimum aquarium size of 24" x 12 x 12" for one adult male Betta  In such a small volume of water nitrate levels will rise quickly, especially when a diet high in protein is being used. Nitrate isn't as toxic as ammonia or nitrite but high levels are still toxic. Even moderate levels of nitrate will affect the fishes fertility and long term exposure could make the fish infertile. To remedy this regular partial water changes are essential, for a small volume of water a water change of 30% once per week isn't excessive, larger volumes of water need less frequent changes and offer more in the way of creating an interesting environment for the Betta.


Betta splendens in a loner by choice. They don't need or desire the company of other Bettas except for a very brief period for mating. If two male Bettas meet they will challenge each other, the challenge is quite ritualized and a fight will only follow if neither backs down. In the wild the loser can easily escape if he feels he is up against a bigger or more seasoned campaigner because the last thing either fish wants is to get injured.

Placing two male Betta in full view of each other especially in close proximity will produce an instant reaction and challenges will be mutually issued. Normally at this stage one fish will decide that the other is the dominant fish and it will try to flee, but it can't, likewise the dominant fish will try to take things to the next level because the weaker fish is still there. It has been shown in behavioural experiments that the fish finds the opportunity to attack another fish rewarding but even if no tissue damage was done, repeatedly stimulating the fish in this way will cause stress and if the situation is long term then it will have an impact on their health. Other fish are tolerated provided that they don't attack the slower and less agile Betta itself.

Bettas like all fish do need some stimulation. Keeping a fish which comes from a densely vegetated area where it hunts alone through the leaf litter in a bare tank surrounded by other Betta is the exact opposite of what the fish really requires. A well planted tank will allow the fish to exhibit all its natural behaviours even if the tank is the minimum recommended size. A fish housed in this way is likely to stay healthier and live longer and will be far more interesting as a result.


Bettas are normally quite adaptable and hardy. Under good conditions they rarely fall ill. But if they are kept in poor quality water, kept too cool, kept in stressful conditions or in water with an elevated bacterial count sooner or later their health will suffer. Typical ailments for fish under stress from one of the listed conditions are: fin rot, poor healing, pop eye, dropsy, bacterial infections and fungal infections. The vast majority of well kept fish rarely if ever suffer from any of these.

Treating the symptoms doesn't help in the long term, only dealing with the cause will effect a cure. Keeping the Betta in water laden with salt or other medication in an effort to lower the bacterial count will only add to the fish's stress and make illness more likely. There is no easy answer when it comes to protecting the health of your Betta other than good basic fish keeping.

Under ideal conditions a Betta splendens will live for 2 to 5 yrs but some manage 8 yrs.

Popular myths

Bettas are able to cope with polluted water.

Not so. Bettas can cope with water low in oxygen due to their labyrinth organ which acts like a primitive lung enabling them to draw oxygen from air.

They cannot deal with nitrite or ammonia any better than any other fish.

Bettas can cope with a wide range in temperature.

True, Bettas can easily cope with a range from 24° to 30°C, (75° to 86°F). They are tropical fish and they have evolved at the warmer end of the tropical fish temperature scale. Keeping them at lower temps will put great stress on them and as a result they are more likely to fall ill to things like:

  • Indigestion, bloating and blockages. Due to poor digestion at low temps
  • Bacterial infections such as fin rot.
  • Fungal infections.
  • Poor healing due to a slow metabolism resulting in tatty fins.
  • Because their immune system doesn't work well enough in low or fluctuating temperatures.

Betta enjoy being able to flare at each other.

Partly true. It has been shown in scientific behavioural experiments that male Betta do enjoy the chance to flare. Betta fights are highly ritualised and always begin with an 'exhibition' of fins. At this point a subordinate fish will have second thoughts and leave the scene before being injured, only well matched males will go on to fight. If the two (or more) are forced into close proximity the subordinate male will not be able to escape and this will place it under a great deal of stress due to the imminent threat of attack and possible death. The dominant fish will also be placed under stress by having a weaker intruder who he can't get at and who won't leave. The result will be that both fish will eventually exhaust themselves and appear to ignore each other.
Ideally the odd reflection or glimpse of a mirror for a few seconds will probably keep the fish stimulated but being forced to live side by side with just a transparent barrier between them is not to be recommended.

To many water changes can be stressful because it removes helpful bacteria and changes the water chemistry.

False. There is little or no nitrifying bacteria in the water column. Only the bacteria which begins the process by converting waste into ammonia are found in any numbers in the water column and these bacteria multiply very very rapidly. All other species of nitrifying bacteria live on a solid surface such as a filter sponge or any and every surface within the aquarium with an oxygen supply. Ammonia is extremely toxic to fish and removing it is essential because leaving it there is more dangerous to the fish than a change in water chemistry.

Female Betta should be kept in a group.

Wrong. Betta are loners, they prefer their own company and other Betta are always regarded as rivals except during spawning for a very short time only. Breeders do keep their females together but only for convenience. Having a large group together will dilute the effects of any aggression but it isn't ideal.

Betta only need a small space.

False. Wild Betta defend a territory approx. 2ft in diameter. This territory will be extremely dense in vegetation and leaf litter. The Betta will spend its entire day either searching through the leaves for food, chasing off any intruders or trying to attract any potential mates. This is very far removed from a tiny barren glass bowl. In a planted aquarium a Betta will remain active, healthy and very interested in its surroundings even without another male to flare at.

Bettas need salt in their water to help prevent disease.

False. Bettas are freshwater fish and adding salt to their water will place a strain on their osmoregulation system and odd as it may seem it could dehydrate them. Salt has its place as a medication for certain illnesses but only for a short time. A healthy Betta in a good environment doesn't need and shouldn't have any salt in their water.
If salt is added on a permanent basis it will lose its effect. The background bacteria will change and they will live in their usual numbers even with salt present (even marine fish suffer from bacterial infections). If the fish becomes infected with a salt tolerant bacteria you have already lost one normally effective remedy.


Avoid: cramped conditions, stress, fluctuating temperatures or cold water and poor water quality.
Provide: A good varied diet, filtration, heating, an interesting environment and you will enjoy an active healthy Betta at its best for several years.


In April 2007 a new animal welfare bill came into force in the UK. The bill places a legal obligation on all pet owners to provide proper care for their pets. Under the bill, proper care is defined as:

  • The need for a suitable environment.
  • The need for a suitable diet.
  • The need to be able to exhibit normal behaviour patterns.
  • Any need to be housed with or apart from other animals.
  • The need to be protected from pain, suffering, injury or disease.

Expert opinion will decide if these criteria have been met should a case come before a court and according to expert legal opinion we will not be able to use the defence that we did not know, or that the fish did not appear to be suffering.. The new law will apply to farmed, domestic, or captive mammals, birds, reptiles, amphibians and fishes.

*Betta = Betta splendens in this article.

Betta Welfare

This article has been written with the welfare of Betta splendens, commonly referred to as a Siamese Fighter fish, in mind rather than in the interest of the Betta hobbyist. If you are a Betta collector rather than a fish keeper with a special interest in Betta then you will probably like this article least of all. But all I ask that rather than dismiss the information some open minded individuals will at least try keeping their fish in the ways recommended and report their findings back to other hobbyists in a true and unbiased way.

Inquisitive Betta splendens

Betta splendens

Betta splendens behaving naturally

Betta splendens live in dense vegetation where they can find all that they need in a relatively small area of about 60cm in diameter. It's far better seeing one active, healthy and behaving naturally than seeing one sat motionless on the floor, doomed to a premature death in a tiny unheated, unfiltered bare glass vase.


Rainboth, W.J., 1996. Fishes of the Cambodian Mekong
Marcus Song, Caring for Betta Fish
Betta splendens" Fishbase.
Betta splendens Wikipedia