Columnaris In Guppies (Treatment, Causes, Prevention)

If you are worried about cotton-like patches forming on your guppies, your guppy fish is likely suffering from Columnaris or saddleback disease.

Columnaris also known as saddleback disease or cottonmouth disease is caused by a bacteria called Flavobacterium columnare. This disease is contagious. This bacteria enters from the guppy’s gills, mouth, or wounds.

Fortunately, your fish’s immune system is strong enough to combat this disease, however, some reasons might lead to your fish’s immune system being compromised. As a result, your fish can catch this disease.

Columnaris In Guppies

One thing to note here is that if your fish catches this Columnaris or “saddleback” disease, the chances of its survival are very slim. That is not to say that all hope is lost, if identified on time and treated properly, your fish can make a full speedy recovery!

There are several, preventable reasons for this disease that we will go through. No need to panic if your fish has contracted this disease, I will go through the most convenient treatments for your fish so that it is not hard for you!

What are the causes of columnaris in guppies or other fish?

As I mentioned above, Columnaris is not a disease that is introduced, it is always present in the fish tank; waiting to strike as soon as the immune system of a guppy fish is compromised. So, the real question here is what weakens the immune system.

While we are on the topic of the causes of immune system failure, I will also give advice or guidance on the measures that can be taken to avoid it.

Poor Water Quality

first and foremost, poor water quality affects the health of fish. A poorly managed fish tank means an over-stocking fish tank, not adding clean water to the fish tank, and inconsistent water temperatures.

  • Overstocking the fish tank means adding too many fishes to it at one time, this is harmful to all the fish. This is because not only will it increase the chances of injuries, but it will also lead to an uneven food distribution, which, consequently, will lead to some fish being overfed and some being underfed. This weakens the immune system increasing the chances of Columnaris.

The Prevent of this is very obvious, either don’t add too many fishes in a fish tank, or if you already have too many fishes, take a few out and move them to a different fish tank, or give them away, always remember, the health of your fish is the priority, even if it is at an expense of a few fishes.

  • Not cleaning the fish tank also causes Columnaris. This is due to the fact that dirty water parameters can have excess ammonia, nitrates, and nitrites which can be extremely harmful to your fish. Too much ammonia can not only cause ammonia poisoning, but it can weaken the immune system of the fish too.
    to prevent this from happening, get an ammonia testing kit from Amazon or any other outlet, and test the fish tank’s water regularly. Make sure the pH is between 6.9 to 7.9, and finally, test the water for nitrates and nitrites.
  • Inconsistent water temperatures also weaken the immune system, this happens because of a number of reasons, firstly, a sudden fall in temperature will slow down the digestive system of the fish. This will lead to many problems, like constipation, which weakens the immune system and makes the guppy fish prone to diseases like Columnaris.
    secondly, a sudden change in the temperature of the fish tank’s water will cause panic in the fish, this stressful situation will lead them to skip meals. Thus, their body will not receive the nutrients it needs to maintain the immune system, which will weaken the immune system and lead to diseases like Columnaris.
    to prevent this from happening, install water heaters in your fish tank to keep the temperature constant.

Poor Diet

A poor diet can also weaken the immune system of a fish and cause Columnaris (saddleback) disease. Guppies are omnivores, which means that they require a diet of meat and vegetables both.

A poor diet does not necessarily mean underfeeding your guppy fish. A poor diet is not having the required nutrients to support the guppy fish’s immune system.

A guppy fish requires a feed of flakes, boiled shrimp, and ringworms. These make the digestive tract move smoothly and also have enough nutrients to support the immune system, otherwise, your guppy fish’s immune system will be compromised and thus your guppy can fall sick.


injuries not only weaken the immune system but the bacteria that cause Columnaris can enter the body through an open wound.

Injuries can be caused by aggressive tank mates or sharp ornaments. Having aggressive tank mates is not recommended for guppies as guppies are very peaceful, they will not attack even if attacked first, so any bullying or harassment they might be subject to, can and will deteriorate their immune system.

Speaking of aggressive tank mates, having aggressive tank mates will encourage the guppies to skip meals and hide from the other fishes. This will further weaken their immune system as their body will not receive enough nutrients.

The way to around this is very simple, remove the aggressive tank mates and move them to a different fish tank, or if it is an ornament that causes harm to your fish, remove it from the fish tank and throw it away. As I mentioned above, the safety and welfare of the fish must be the top priority, so losing an ornament that you spent money on should not be a problem.

The Stress Caused by Shipping and Handling

moving your fish from one tank to another can be a very stressful experience for your fish. This is because the quick change in the water environment and parameters makes it difficult for them to adjust.

This stress can also cause your fish to stop eating, or skip a few meals, which will weaken the immune system of the fish making it prone to diseases like saddleback disease (Columnaris) You can avoid this by making the new tank as close to the previous tank as possible, this will make it easier for them to adjust to the new environment.

Symptoms and Identification of Columnaris or Saddleback Disease

Fortunately for you, identifying Columnaris is very easy so chances are that you are going to spot this disease before it gets serious. The main thing to look out for is cotton-like patches forming across your guppy fish’s body, primarily its mouth.

However, there are other symptoms of Columnaris too, so keep an eye out for those too. This is because just the cotton patches also seem like fungal infections so it is easy to confuse both.

Frayed fins

You might begin to notice frayed fins in your fish if it is suffering from Columnaris. This means the edges of your fish’s fins will appear to be tattered, this can happen to the gills of your fish too.

Lesions Start Forming on their Skin

Starting off looking like a greyed-out area or patch that lacks shininess, and ends up developing into sores and infections. These can be lethal if developed fully. Therefore, you should always keep an eye out for any discolored patches in your fish as it can be an early stage of illness.

The Fish will Rub against Things

If you notice cotton-like infectious marks on your fish, so does your fish, and they will do anything they can to get rid of it. This includes rubbing against things.
this can also be the reason behind the lesions forming or a few scrapped-off fins.

Greyish Cotton-Like Spots appear

This is the main symptom of Columnaris, which gives it the name, cotton wool disease. Sometimes, the cotton-like patches appear behind their back looking like a saddle, hence giving it the name, saddleback disease.
these patches usually form around the mouth of a fish but they can appear anywhere else too.

Deterioration of the Mouth of your Guppy

If your fish has contracted Columnaris or saddleback disease, you might begin to notice that its mouth is starting to corrode, this develops in the later stage of Columnaris or saddleback disease. In the worst-case scenario, your fish’s mouth will fall off.

How to Treat Columnaris in Guppies?

Columnaris is a dangerous disease, and the chances of your fish surviving it are very slim. If your fish contracts this disease, unless you are sure that you can help it, the best option available is euthanasia

However, let’s not lose hope, there are a few remedies available for Columnaris. However, you have to be very careful to go about this, anyways, follow the following steps:

Quarantine your Infected Fish

The first thing that you are going to want to do is move the infected fish from the main fish tank to a different, quarantine (or hospital) fish tank. Doing this will not only avoid the spreading of this disease, and eventually a pandemic, but it will protect other fishes from the substances in the medication that might otherwise be harmful to other fish. Doing this will also ensure a safe place for your guppy fish to rest. As usual, the weaker fishes are subject to harassment and bullying, which might further deteriorate their health.

Test the Water Quality

To make sure that other fish in your care do not contract this disease, check the water quality. Check for any ammonia, nitrates, nitrites etcetera. If there happens to be any excess, use detoxes to detox the water.

Cool the Water Down

Cooling down the fish tank’s water will slow down the growth and reproduction of the bacteria responsible for Columnaris. However, keep a few things in mind before doing this. Make sure you don’t turn the temperature down too quickly, doing so will cause panic and the stress resulting from the panic will lead to your guppy fish skipping meals. Which will further deteriorate their situation. if your temperature exceeds 75 degrees or goes any lower than 72 degrees, it can be fatal for your fish.

Begin Dosing

The final and most important step would be dosing your fish with the right amount of medicine. To start, remove the chemical filter from your fish tank as that can reduce the effectiveness of the medicine. After that, use antibiotics (like Kanaplex) to help the fish. Make sure to read the backside of the box to only give the prescribed amount to your fish. Overdosing will do more harm than good. If your fish has a severe infection, repeat it a few times gradually for 2 days. If it persists after 2 days, there is nothing that can be done, euthanizing it is the only option left.


One important thing to keep in mind is that it is always a wise decision to quarantine any new fish that you buy. This is because sometimes the disease can take time to be apparent, adding the fish directly to the fish tank will infect other fish too, if your fish is infected. This is why you should always purchase fish from reputable retailers who keep a check on the health of their fish.

Another thing to note down is that guppies are peaceful creatures. They will not attack other fish even if attacked first. So, either remove all your guppies from a fish tank that contains aggressive fish or remove the aggressive fish from the fish tank and transfer them somewhere else. This will eliminate the chances of your fish getting injured.

One final thing to note is that you should always disinfect any ornaments that you add to the fish tank. this will get rid of the bacteria in them and therefore, will not be harmful to your fish.

A word on Euthanasia

If you have tried everything that you can to cure your fish but nothing has worked, the only humane and possible thing left to do is euthanize your fish.

Euthanasia is a hard decision especially if you have gotten close to your fish. However, in order to put your guppy fish out of its misery, you have to put it down.

There are many ways that can be used to euthanize your fish. The most common and convenient method that people use is boiling or freezing their guppies. Although this is very easy for a human, the fish goes through immense pain before finally passing, therefore, most people consider this inhumane. Some people also flush the fish, still alive and suffering, down the toilet. Thinking it will die on its own. However, freshwater fishes can not and do not survive out in the open, they will fall prey to any predator. Dying out in the sewers is a slow and painful death.

The best method, that I use, is the most humane and the fish barely feels a thing. You start off by removing the fish from the main fish tank and placing it in a different container. After which, you are going to add clove oil in high concentration, make sure you do it gradually as a sudden change in the environment will scare the poor fish. Within a few seconds, the fish will pass and you can dispose of it by either throwing it in the trash or flushing it down the toilet.

One thing to remember is that you should always wear protective gear when disposing of dead fish, or when moving sick fish from one place to the other. Since there are many diseases that a contagious and humans can catch them too. Wash your hands before and after handling the fish.

The Bottom Line on Columnaris In Guppies

In conclusion, Columnaris is a dangerous disease, it can be fatal for your fish if not taken care of on time, or properly.

There are many causes that lead to Columnaris, the main reason that leads to Columnaris or saddleback disease is a compromised (weakened) immune system. There are many reasons for a weakened immune system, from poor quality water parameters to poor diet. Fortunately, treatments are available for this disease, and they are somewhat simple.

That being said, as always, prevention is always better than cure, there are a lot of measures that can be taken to prevent this disease. For example, providing a good diet, removing aggressive fish or ornaments, and quarantining new fish. Happy fishkeeping!!!!

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