Betta Fish and Diseases

In this blog, we will learn a little about the main diseases in betta fish, their causes, prevention and treatment. This is of utmost importance for fish health and will help beginners to better understand the dynamics of the main diseases in betta fish.

Betta Fish Behaviour When Sick

If you have a sick betta fish, you are undoubtedly afraid, perplexed, and worried about how this happened. Betta fish, while reasonably resilient, can succumb to parasitic, bacterial, and fungal infections much like any other freshwater fish. This condition can be fatal to some delicate fish species, such as bettas.

Quick detection and treatment will reduce any harm and get your colourful companion swimming joyfully again. The best method to keep your betta fish healthy and happy is to provide adequate betta fish care. It’s always preferable to be proactive rather than reactive.

Here are some of the behaviours that a sick betta displays:

  • Lethargic: Inactive, languid, lacking aggressiveness, and prefers to remain hidden.
  • Refusing to eat for long periods of time (e.g. days)
  • Fading hues, particularly in male bettas
  • Breathing is difficult.
  • Damaged fins
  • Fins tangled

Certain actions are associated with a stressed or unwell betta fish, but not always with a full-fledged sickness. The simplest approach to know whether your betta fish is unwell is to identify these characteristics. It is critical to recognize these habits and address the issues as soon as possible. Let’s analyse some diseases below.


Columnaris is a fungal infection observed in the tropical fish keeping hobby that is also known as Cotton Wool disease or Saddleback sickness (and is even more common in the commercial aquaculture markets). Columnaris infection is caused by bacteria, is easily transmitted, and is fatal if untreated.

Columnaris is caused by the bacteria Flavobacterium columnare. It is a widespread freshwater species that comes into touch with colder air (53 to 57 degrees Fahrenheit), such as ponds. Flavobacterium columnare is so widespread that it may be found in almost any freshwater. This includes the water used to fill fish tanks.

Why does the bacterium only impact fish under particular conditions if it already exists in the fish tank? How can Columnaris make a fish sick? A Saddleback disease epidemic is usually caused by one of the following conditions:

  • Bio-loads that are greater than your filtering system’s capacity
  • Overcrowding in your Betta aquarium
  • Dissolved oxygen levels in the water column are lower.

The nitrogen process in your aquarium is often referred to as a bio-load. Waste from your Betta fish, as well as uneaten food, contribute to the nitrogen cycle. Decomposed leftovers can also be a source of increased nitrates in fish tanks with many pets. Some by-products are also harmful for fishes.

Nitrate is a by-product of nitrite oxidation during the latter stages of the nitrogen cycle. In nature, nitrate in water remains very low, generally well below 5 ppm. High nitrate levels are especially harmful to fry and young fish and will negatively affect their growth.

Nitrate levels as low as 10 ppm will promote algae growth.

Because most enthusiasts retain solely Siamese Fighting fish in their tanks, a significant bio-load may grow unchecked. Betta owners frequently utilise smaller aquariums, where nitrate levels can have an immediate impact on water quality.

The absence of dissolved oxygen in the water column is another factor that causes Columnaris infections. Before entering the bloodstream, dissolved oxygen (DO) penetrates your fish’s gills. In small Betta aquariums, low DO is possible since owners don’t often identify the issue.


Dropsy is an archaic medical name for edema or ascites, which are more commonly used nowadays. The word hydropse comes from the Middle English word dropesie, as well as the Old French word hydropse and the Greek word hydropse. Dropsy in fish is a slew of symptoms brought on by a bacterial infection found in aquariums.

Fish with an underlying bacterial illness can have a wide range of characteristics. Some people will have a large tummy, while others will have skin sores, and yet others will have no symptoms at all. In most situations, a variety of physical and behavioural signs are noted.

Fish are only vulnerable if their immune systems have been weakened by another stressor. It’s rather typical for the entire tank to become sick if all of the fish in the tank are stressed, but it’s also conceivable for only one or two fish to become unwell, especially if immediate action is done to prevent the infection from spreading.

Symptoms of dropsy: 

  • a stomach that is grossly enlarged
  • Scales having a pinecone-like look that stand out
  • Eyes that swell
  • Gills that are light in colour
  • The anus that becomes bloated and red
  • The faeces are pallid and stringy.
  • Ulcers along the lateral border of the body
  • Fins that are clasped together on a curved spine
  • Skin or fins that are red
  • Lethargy in general
  • Refusal to consume food
  • Swimming along the water’s edge

The Aeromonas bacteria, one of several gram-negative bacteria found in most aquarium settings, is frequently the culprit that produces dropsy symptoms. The bacteria are referred to as gram-negative because they do not react to a specific stain used to identify bacteria species using the Gram Stain technique.

The infection that causes dropsy is difficult to treat. To prevent the virus from spreading to healthy fish, some specialists propose that all afflicted fish be euthanized. The outlook is also grim when paired with Popeye. It is possible to save infected fish if the infection is diagnosed early and the fish are segregated for effective treatment.

Hole in the head

Hexamitiasis is a parasite infection that affects both freshwater and saltwater fish. Lesions form on the head and flanks of the fish in some cases, earning it the nickname “hole in the head illness.” Head and lateral line erosion (HLLE) illness in fish could be caused by Hexamita infections.

Hexamita-infected fish produce white, stringy faeces and have a more muted colour than normal. The fish lose their appetite and become malnourished as time goes on. Lesions on the fish’s head occur frequently, but not always. These lesions can occasionally be seen on the flanks of the fish.

Hexamitiasis is caused by various species of the protozoan parasite genus Hexamita. Parasites are likely present at low levels in the intestines of many aquarium fish where they do no harm. How and why the parasites are able to switch from their normal intestinal form into the systemic form is not known.

Metronidazole is the most common treatment for hexamitiasis. Medicated fish food is the most effective treatment, especially related to early infections. However, if the fish are severely damaged, you should add the drug to the water once a day for at least three days, at a dosage of 250 mg per 10 US gallons.


Protozoan parasites, particularly those that cause white spot disease, are the most common parasitic infections. In freshwater tank fish, white spot disease is a widespread condition. Ichthyophthirius multifiliis, often known as ich or ick, is a ciliate protozoan that causes the disease.

Small, blister-like elevated lesions (white patches) appear on the skin and/or fins of ich-infected fish. However, if the infection is limited to the gills, no white patches will appear. Ich infects nearly all freshwater fish and causes a high incidence of mortality. In a short amount of time, all of the fish in a tank might be easily destroyed.

Fish are most likely infected by the parasite ich. Immediate treatment is required in order to save the infected fish. Parasites can reproduce rapidly, and one mature ich trophont can produce several hundreds to thousands of infective theronts at a water temperature of 22° to 25ºC (72º to 77ºF).

The best method for controlling infection is prevention. Precautions are needed when establishing an aquarium to prevent ich from being carried by fish, aquatic plants, gravel, and water. Fish should be quarantined in a separate tank for at least a week to 10 days before adding them to the main aquarium.

Fish that survive an ich infection develop an immunological response and become resistant to re-infection. Antibodies against the parasite can be found in the serum and mucous of those immune fish. Anti-ich antibodies cause infective theronts to become immobilised when they come into contact with anti-ich antibodies.

Tail Rot

Betta fin rot and tail rot (melt) is a gram-negative bacterial infection or fungal infection that is extremely prevalent in betta fish. More common in uncycled tanks and small bowls, fin rot attacks and begins to eat away at a betta fish’s beautiful fins. Many bettas from large box stores may show signs of fin rot due to water quality.

First and foremost, do not be alarmed; fin rot is quite common and rarely fatal. It is the most frequent disease among the species, and it is caused by bacteria found in the water of your aquarium. These bacteria become a concern only when your betta’s immune system is compromised, which you may treat to prevent further outbreaks.

Poor water conditions are the most common cause of fin rot in betta fish. If the water tank is hazy, full of uneaten food, and globs of faeces, with a temperature way below 78 degrees Fahrenheit, a cold water, high ammonia (>0 ppm), nitrite (>0 ppm), and nitrate (>20 ppm) levels all cause stress and damage the immune system of betta fish.

Fin rot can be classified into phases ranging from minor to severe, each with its own set of symptoms and severity. It’s usually better to notice any obvious signs or symptoms of fin rot early because it can spread swiftly if left untreated. If your betta has fin rot, the Dorsal (top), Caudal (tail), and Anal (bottom) fins are the simplest to check and identify.

The most prominent symptoms are as follows:

  • Brownish fin edges, ragged fin edges, white tips or patches are all signs of mild fin rot.
  • Moderate Fin Rot: Large fin degeneration and receding, black or bloody fin edges, fins developing fuzzy growths.
  • Severe Fin Rot: Inflammation and redness of the fin base, bloody fin bases, complete loss of fin or fins and fin membranes.

The earlier you catch betta fin rot, the easier it will be to treat. If your betta lives in a tank larger than 2 gallons or with any other living things (including plants), you should confine it right away. A smaller quarantine tank is usually preferable because it is easier to provide medication and change the water.

If you’re going to be keeping a betta in a quarantine tank then the first step is to acclimate your fish before adding it directly to the tank. If you have a filter then you can do partial water changes, 25% of water every 72 hours should be sufficient. But if you’re not doing this then you’ll need to do a complete water change.


There are several diseases that affect betta fish, and there are many ways to treat them. In this blog, we learn a little more about the most common ones. It is important that the aquarist be aware of the health of his fish and always ready to take preventive and corrective actions.

Frequently Asked Questions (FAQ) about Betta Fish and Diseases

What are the signs that your betta fish is sick?

The majority of Betta ailments, on the other hand, are caused by poor water quality or a bad diet, so make sure you’re doing these things correctly. Health Issues:

  • Fin Rot: The tail or fins appear to be torn.
  • White dots on the body of the fish.
  • Velvet: The fish isn’t eating or clawing itself against the tank’s objects.

What is the best way to treat columnaris in betta fish?

Antibiotics, chemicals in the water, or both should be used to treat external infections. To cure columnaris, copper sulphate, acriflavine, furan, and terramycin can all be used in the water. Terramycin has been shown to be useful as a bath and in the treatment of internal infections in foods.

Is it possible to get rid of dropsy?

Dropsy is a difficult condition to overcome. The goal of treatment is to address the underlying issue while also providing supportive care for the sick fish. A broad spectrum antibiotic developed specifically for gram-negative bacteria, such as Mardel Maracyn® 2, is indicated. Always follow the guidelines for dosage and duration.

How long does it take for ich to leave?

Some people in the fishkeeping community feel that ich can be found in any tank with fish. In any case, you’ll want to respond quickly if it makes its way into your tank. Thankfully, therapy is usually beneficial, but you should plan on treating the affected fish and water for a few days to a week.

How do you treat betta fish tail rot?

Erythromycin, a broad-spectrum antibiotic that is effective against fin rot. Methylene blue is an effective antifungal treatment if your fish has developed a secondary fungal infection. To ensure a speedy recovery, keep your fish’s habitat clean and pleasant.


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