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Betta Fish Diseases

If your fish is well cared for then disease should not occur very often. When your fish do become ill you should act immediately. This topic is so broad that I can only give a general outline here. As ominous as these diseases sound you should be aware that most are easily treatable if you recognize the signs and treat your fish quickly. As always Prevention is the best cure.

You might want to Bookmark this page so you will have quick access in case of a future emergency.

It should be noted that this is for your general knowledge and while all attempts have been made regarding accuracy of content we can not be held responsible for any action taken on your part as a result of this information. You should always consult a qualified expert in the care and treatment of your fish.

In general fish diseases can be catagorized as either Environmental, Bacterial or Parasitic.

Environmental has everything to do with the condition and set up of your fish's home. A well maintained fish tank or bowl will virtually eliminate these types of diseases.

Bacteria exists in all tanks and in most cases this is not a bad thing. However when your Betta is stressed some bacteria can and will infect your fish and cause its health to decline. This is usually a slow process but in some cases it can spread rapidly leading to the death of one or more of your fish in a matter of hours.

Parasites are tiny creatures that feed off of your fish. The most common parasite is known as Oödinium and the little buggers can strike down every fish in your tank.

Below are listed some of the most common forms of these 3 Diseases.

Unionized Ammonia (NH3)



Ammonia poisoning can occur for any or all of the following reasons and is probably the number one cause of death in cultured fish.


When a tank is newly set up.
When you add too many new fish to a tank at one time.
When the filter fails.
When bacterial colonies die off because of medications or sudden changes in water conditions.


Fish gasp for breath at the water surface.
Purple or red gills. (Fish appears to be bleeding)
Fish is lethargic
Loss of appetite
Fish lays at the bottom of the tank
Red streaking on the fins or body

Ammonia poisoning can take days or appear suddenly.Usually you will notice your fish gasping for air at the waters surface.Since it is not uncommon for Betta fish to breath on the surface, it is important for Betta owners to know their fish in order to spot the changes. The gills may appear to be bleeding by turning a reddish or lilac color. The most obvious sign you will notice is that your Betta will become very lethargic and stop eating. Sometimes your Betta will simply close its fins and lay on the bottom of the tank.

If untreated the poisoning will eventually do tissue damage which will appear as red streaks or bloody patches on the body and fins. Internal damage occurs to the brain, organs, and central nervous system. Unchecked your Betta will hemorrhage internally and eventually die.


Lower the tanks pH below 7.0
Change 25 - 50% of the tanks water. (use aged water)
Apply neutralizing ammonia chemical like AmQuel (available at pet supply store)
Reduce feeding. (the uneaten food will only increase problems)

Kordon AmQuel

Using your test kit;

Begin treatment immediately if the ammonia level rises above 1 ppm.
Lower the pH of the water to provide immediate relief.
Change 50% of the tanks water.(be sure to use aged water and make sure that it is the same temperature as the aquarium).
You may need to change water several times over a short period to drop the ammonia to below 1 ppm.
Only use the neutralizing chemical if the fish are in severe distress.
Restricted feedings to reduce waste.
If the ammonia levels are extremely high then discontinue feedings outright. (sometimes for several days.)
Do not add new fish to the tank until ammonia and nitrite levels have fallen to zero.

Testing ammonia and pH levels are critical. Ammonia toxicity increases as the pH level rises above 7.0.

If you don't have a test kit I find this kit is easy to use and tests for pH, water hardness, alkalinity, nitrites, nitrates and ammonia in both freshwater and saltwater tanks.

Mardel Master Test Kit

To set and stabalize your pH use Aquarium Pharmaceuticals Proper pH

One product that I like sets your pH level to7 and eliminates ammonia at the same time is Neutral Regulator from Seachem

General rules of thumb.

Your fish are under stress as soon as a level of 1 ppm or 1 mg/l of ammonia is detected even if they show no outward appearance of being stressed. Even levels  lower than 1ppm can cause your fish to die if they are exposed to ammonia for a prolonged period. Do not stop daily tests and treatment until the ammonia drops to zero. Unfortunately you may still lose some fish even after the ammonia levels drop off as the fish was exposed for too long.


The key to avoiding fish death from ammonia poisoning is to avoid ammonia spikes in the first place. To do this you should;

Stock new tanks slowly.
Avoid overstocking.
Do not overfeed and remove uneaten food after 5 minutes.
Change water regularly (The more populated your tank the more often the change)
Test water for ammonia at least twice a month.
If the filter stops, test for ammonia twenty-four hours later to ensure that the bacterial colonies that eliminate wastes were not affected.
Anytime a fish appears to be ill, test for ammonia to rule out ammonia poisoning.
Clean the tank weekly.

If your ammonia levels stay high then use Jungle Labs Ammonia Chloramine Eliminator: ACE to quickly convert ammonia to its nontoxic form.

Nitrite Poisoning


Also know as: Brown Blood Disease, Nitrite


After ammonia, nitrite poisoning is the major killer of cultured fish. Be warned that if you have had ammonia problems then the nitrite levels will rise as well and your fish will be at risk from this new threat. Anytime ammonia levels are elevated you can be sure that elevated levels of nitrites will soon follow.


Fish gasp for breath at the water surface.
Fish hang near water outlets trying to obtain more oxygen.
Rapid gill movement (oxygen)
Fish become lethargic.
Gills take on a brownish hue.

The same precautions apply to nitrite poisoning as ammonia poisoning.
Always test levels;

When setting up a new tank.
When adding new fish to an established tank.
When the filter fails.
When applying medications to your fish.

The reason this disease is also known as 'brown blood disease' is because the blood takes on a brown hue from an increase of methemoglobin. Besides changing the blood's color, methemoglobin reduces the blood's ability to carry oxygen which will eventually cause the poor fish to suffocate.

Nitrite poisoning affects species of fish differently. Some species will die suddenly without showing any signs of illness while other species may only become lethargic.
Those that become lethargic run the risk of secondary problems if exposed to nitrite for extended periods of time. Their immune system weakens and increases the likelyhood of developing diseases such as bacterial infection, fin rot and ich, to name just a few. If left untreated all species will suffer gill, blood cell and liver damage as a result of the methemoglobin levels and eventually they will perish by suffocation or one of the secondary diseases.


Large water change
Add one half ounce of salt/gallon of water (preferably chlorine salt) to prevent methemoglobin from building up.
Reduce feeding.
Aeration should be increased to saturate the water with oxygen.
Do not add new fish to the tank until ammonia and nitrite levels reach zero.
Test daily until nitrite is completely gone. (Nitrite is far more lethal at low levels than ammonia so it is imperitive that you get it to zero before you stop daily testing.)


Stock new tanks slowly
Feed sparingly and remove uneaten food
Change water regularly
Test water regularly to catch problems early
Always test the water for nitrite after an ammonia spike has occured as there will be a nitrite increase later.

The same prevention proceedures apply for nitrites as you would use for ammonia.

For detoxifyng nitrite and nitrate in your tank you might want to invest in a product like Seachem Prime for Freshwater and Saltwater

Flexibacter columnaris


Also known as; Cotton-Wool, Cotton-Mouth, Flexibacter, Columnaris, Mouth Fungus.


Often mistaken for a fungal infection because of its mold-like lesions, Columnaris is a common bacterial infection in cultured fish, particularly livebearing fish and catfish. Its name is derived from columnar shaped bacteria, which are present in virtually all aquarium environments.

When fish are stressed by poor water quality, poor diet, or even handling and shipping, they become prone to bacterial infections. Columnaris enters the fish through the its gills, mouth, and even through small skin wounds. The disease can spread rapidly in nets, holding containers, food or any number of other means. It is highly contagious.

In chronic cases, lesions will appear slowly and can take many days before killing your fish. An acute infection can spread quickly and will often kill off an entire fish population, sometimes within a few hours.The disease progresses quickly in high water temperatures but, unfortunately, lowering the temperature will not prevent the eventual outcome. Columnaris can be both external and internal.

External Symptoms:

White spots ( paleness) will appear first on the mouth and the edge of fins and scales. Later the lesions become brownish/yellow and may have a red tinge around them.
The mouth will form a growth that looks like cotton (or moldy looking) which eats away at the infected area.
The fins begin to erode from the edges inward.
The area near the dorsal fin will develope a lesion which has the appearance of a saddle.
The affected skin becomes covered with fungus.
The filaments in the gills begin to erode and the gills start to move rapidly trying to obtain oxygen.
While less common, the infection can be internal which displays no external symptoms.


Change water
Vacuum gravel (bacteria thrive on organic wastes)
Add aquarium salt (enhances gill function)
Treat with copper sulfate,antibiotics and chemicals (Acriflavine, Furan, and Terramycin)
Discontinue carbon filtration during treatment
Terramycin is effective in treating foods for internal infections.
Use caution when treating catfish, as many are sensitive to salt.


Quarantine new fish for two weeks
Maintain high water quality
Provide fish with a nutritionally balanced diet
Medicate fish prophylactically before moving them
Always disinfect all equipment before each use to avoid spreading the bacterium.

Remember, a proper diet and maintaining good water quality in general will keep the fish from being stressed and therefore reduce its susceptibility to infection.

Oödinium pilularis

Parasitic skin flagellate

Also known as, Rust, Gold Dust Disease, Oödinium, Velvet


Oödinium is one of the more common diseases in cultured fish. This tiny parasite is capable of decimating an entire fish population, usually before you realize what the problem really is. It strikes both fresh and saltwater fish equally.

In freshwater fish Velvet is caused by either Oödinium pilularis or Oödinium limneticum. In marine fish Oödinium ocellatum causes Coral Fish disease. All three species are similar to the well known parasite, Ich.

Oödinium uses flagellum to adhere to fish and then forms rod pseudopodia which penetrates the skin and gill filaments. This destroys the cells and allows the parasite to feed on the nutrients inside. Eventually the parasite matures and divides into dozens of cells that drop off the original host and spread out in the tank in search of new hosts to feed on. They will die within a day if they fail to leach onto another host. They produce a white pustule on the host not unlike Ich but much finer. Sadly they are usually not seen in time and the host dies. Also, not unlike Ich, they are a common occurance in most pet store tanks but only become lethal when fish are stressed. (Poor water quality, temperature changes, handling etc.)


Fish will scratch themselves against hard objects. (Trying to dislodge parasite)
Fish becomes lethargic
Fish display a loss of appetite.
Fish loses weight.
Fish displays rapid gill movement. (a universal sign of illness)
Fish clamp fins against body.
Fish developes a yellowish or rusty colored film on its skin. (telltale symptom - though hard to detect, try a flashlight beam on the fish in a dark setting. Look on the fins and gills.)
Fish's skin will eventually begin to peel off.

This parasite effects all fish, from fry to the aged but is particularly enamoured with Anabantoids, danios, goldfish, zebrafish, and killifish.


Oödinium is highly contagious and is usually in an advanced stage by the time you diagnose it, as such, it is important to take steps to treat it as soon as possible.
Raise water temperature (82 F will speed up the treatment)
Dim lights for several days (Oödinium is dependant on light)
Add aquarium salt (to aid the fish's breathing)
Treat with copper sulphate for ten days. (Atabrine -'Quinacrine hydrochloride', can also be used) The treatment is aimed at the free swimming parasite.
Discontinue carbon filtration during treatment. (carbon filters will remove the drugs from the water.)


Quarantine new fish for two weeks. (They will carry the parasite from the pet store)
Maintain high water quality
Provide fish with a nutritionally balanced diet

Ichthyophthirius Multifilis


Also known as Ich or White Spot


The name translates to "fish louse with many children", a title that fits well, as each parasite may produce over a thousand offspring. Although the disease is the equivalent of a skin infection, it can easily be fatal to a fish stressed by poor diet or habitat.


Small white spots.
Fish scratch against hard surfaces (attempting to rid itself of parasite)
Fish become lethargic (advanced stage)
Fish will eventually develope redness or bloody streaks (advanced stage)

Severe infestations are easy to spot, but small occurrences often go unnoticed at first. Fear not for Ich becomes obvious eventually.

Ich feeds on blood and dead epithelial cells. As the parasite burrows into the fish it causes the skin of the fish to swell and produce white cysts which are seen as a small spots.
After several days, fat and swolen, the parasite lets go of the fish and sinks to the bottom of the tank. The Ich forms a protective membrane around itself and then proceeds to divide into hundreds of baby parasites. These are known as tomites. These tomites repeat the parasitic process and search out a fresh fish to chow down on. It is during this free-swimming stage (3 days tops) that medication must be administered. Once the Ich has found a new fish to call home it is protected from chemicals in the water.


Raise water temperature (speeds up treatment shortens the time it takes for the parasite to reach the stage in which it is susceptible to medication. )
Medicate for 10-14 days (long enough to wipe out all the parasites)
While nothing can kill the parasite whileit is feeding on the fish, the following are effective at killing Ich while it is free-swimming; malachite green, methylene blue, quinine hydrochloride, and mepracrine hydrochloride.
Reduce medication when treating scaleless fish (watch for secondary infections when fish have damaged skin)
Follow dose instructions on package but cut in half when treating scaleless tetras or catfish.
Discontinue carbon filtration during treatment. (removes medication from water)
Perform water changes between treatments.

Methylene Blue

For help in repairing your fishes natural slime coating or damaged skin you can try Biospheres Stress Therapy from Mardel.


Quarantine new fish for two weeks
Treat plants before adding to tank (they can carry Ich  cysts)
Maintain high water quality
Provide fish with a nutritionally balanced diet
Avoid temperature fluctuations.


This may seem obvious but remember that your fish does not like stress. Apart from all the other diseases that can affect your happy little friend stress can also cause death. Always pay attention to how your fish reacts when you add new fish or plants or change anything in the tank. If abnormal behaviour comes about then re-trace your steps and eliminate whatever it was that caused your fish to stress out.

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