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Known by a number of names, columnaris is unfortunately very common among many different types of fish. If you own one or several betta fish, you will want to keep in mind the prevalence of this disease among them. This is one disease that can be absolutely devastating to them on a variety of levels.

At the same time, treating columnaris betta is not impossible by any means. If you understand the symptoms, as well as the different treatment options available to you, columnaris in Bettas can often be stopped, before it causes too much damage. There are also preventative measures that can dramatically decrease the likelihood of columnaris ever occurring.

As mentioned before, columnaris is known by several different names. Some refer to it as cotton wool disease. Others call it saddleback disease. It is also sometimes known as mouth rot or mouth-fungus. However, it is NOT a fungal infection. It is in fact a bacterial infection that can be external or internal. It can also be either chronic or acute.

Why is it mistaken for a fungal infection? This is likely due to the presence of lesions which can appear on your betta fish. They are mold-like in appearance.

Some even refer to the infection as guppy disease. However, it is important to remember that we are talking about a disease that can cause problems among numerous fish types. Regardless of the name, understand that we are talking about a very common type of bacterial infection. It can be found in many different types of aquarium fish, including bettas.

While columnaris bacteria is a little more common among livebearers than fish like bettas, it is still something they are quite susceptible to. If you are planning to own one or several betta fish, you will need to be on the lookout for symptoms, as well as what to do about those symptoms.

What causes columnaris? There are a few different culprits that you will want to keep in mind.

The Most Common Causes Of Columnaris in Betta?

Before we learn more about columnaris symptoms, we should first take a look at what causes this infection in the first place. While it can indeed be devastating, some of the most common reasons for columnaris among betta fish are quite preventable on your end.

The name of the game with columnaris ultimately comes down to stress. There are other ways in which betta fish can catch this infection, which we will discuss in greater detail below. However, you will still notice stress is a consistent factor among many of the most common columnaris bacteria causes:

An Overstocked Tank

Generally speaking, it is suggested that you have one gallon of water for every inch of fish. This is why we often suggest getting a tank in the 15 to 20-range. Unless you have no plans to own more than one or two fish. If you have too many fish in the tank, you’re going to run into some problems.

When you have too many fish in your tank, an overabundance of bioloads is created. When this occurs, your filter can become overwhelmed with its task of trying to keep waste out. This can cause your tank to become too filthy for your bettas to comfortably live for longer.

Poor water parameters can create a breeding ground for bacteria. This will be even more apparent if you don’t have a filter for your tank.

Columnaris is just one of the infectious bacteria that can become prevalent in your tank.

Harassment From Other Fish

This is one of the most common causes of how Columnaris infection can come from stress. All it takes for your betta fish to catch this infection is a weakened immune system. A dirty tank can cause this weakness, but stress is one of the biggest culprits you need to keep an eye on.

Harassment from other fish can very easily lead to columnaris in Bettas. It is rare that other types of fish will bother your bettas, but this is still something that can occur. What is more likely is that your betta can be harassed by other bettas. Male bettas can pick on other males, but they also have a terrible reputation for bothering females to the point of weakening their immune system through stress.

When the immune system is diminished, the odds of your bettas developing columnaris can skyrocket. We would suggest keeping only one betta, and then keeping an eye on their interactions with any other fish in your tank.

It is not impossible by any means to keep a male and female betta together, but it can lead to problems when not properly monitored.

Inconsistent Temperatures/pH Levels In The Water

This is another example of a common columnaris cause that can are easy enough to prevent on your end.

Simply put, bettas need certain levels in the tank to be happy. The good news is that you have a fair amount of wiggle room for both pH levels and temperature. Bettas have a great reputation for being a fairly durable fish.

That said, you still want to keep your tank levels between 76F and 82F for the temperature. On the pH side of things, you want to opt for around 5 to 8. These are not difficult levels to maintain, but it can get complicated, if you add different types of fish to your aquarium.

Check your tank levels. If your betta are not happy with the temperature/pH levels, they will become stressed out. As is the case with the bullying element we mentioned above, this stress can cause weakness to the immune system. This in turn creates the conditions for columnaris.

Poor Water Quality In General

This can actually be an entirely different problem, as opposed to the tank becoming filthy due to overpopulation. Even if your tank is not overstocked, you can still run the risk of conditions becoming unsanitary to the point of elevating the risk of columnaris.

Regular water changes are essential for the health of your fish. This certainly extends to your bettas. A filter is generally the best way to take care of your fish, but the filter still needs to be checked on a regular basis. You also need to make sure the water is changed consistently, as well. The rule of thumb in this arena is to have around thirty to fifty percent of your water changed every week.

Poor water quality can definitely impact your betta fish, leading to a weakened immune system.

And while it isn’t directly related to poor water quality, you should also make sure they are getting the best possible betta fish diet, as well. They are carnivorous fish. This means they should be eating small animals like bloodworms, daphnia, mosquito larvae, brine, worms, and more. The emphasis on good betta diet comes down to making sure they get plenty of protein and living animals to eat.

Brought From Another Tank

One of the most common questions about bettas and columnaris is whether or not it can be passed on from one fish to the next. The answer to this is an emphatic yes. More importantly, it doesn’t have to be a betta that can transfer the infection to another betta. Any fish can give cotton wool disease to another fish.

Quarantining your new fish in hospital tank is always, always a good idea. The window for this is anywhere from two to four weeks.

What Are The Most Common Symptoms Of Columnaris In Bettas?

AS we mentioned earlier in this article, the presence of lesions along the mouth is a certain sign that your betta has columnaris bacteria. The presence of these lesions can appear slowly with a chronic case of the infection. The lesions can spread much more quickly with an acute situation. This can lead to your entire fish tank being wiped out by the bacteria in a matter of mere hours.

Worse yet, if the temperature of the tank is too high, this can exacerbate the spread of the bacteria. This is one of the most visibly distinctive symptoms of columnaris. If you notice these lesions on one or several of your fish, take steps to remedy the situation IMMEDIATELY. Lowering the temperature in the tank is NOT a solution, but it can slow down progression somewhat.

Beyond lesions, there are a few more symptoms you are going to want to look out for:

  • The presence of white spots or gray-in-appearance spots. These can also appear on your betta in the form of patches. Look for such spots along the head. You can also find them around its gills or fins. If your betta fish has bright, beautiful colors, as is commonly the case, you should pay attention to areas that are paler in appearance. As time goes on, these spots can be come yellow or even brown.
  • Look for lesions that go all the way down the sides of your betta. This common symptom is where the name saddle back disease comes from.
  • If you see lesions around the mouth, they will have an appearance not unlike that of mold, which is why the infection is misunderstood by some. If the condition is not dealt with quickly enough, the lesions will eventually become areas that have simply become eaten away by the infection.
  • As the infection worsens, you will also see various forms of damage to the fins. Erosion can occur, which in turn will give the fins a frayed, damaged appearance.
  • Even the gills of your betta can be impacted by columnaris. If you see your betta breathing more rapidly than usual, then it is likely that they are experiencing one of the symptoms. However, by this point, you will have likely noticed the spots and lesions.

In fairly rare cases, cotton wool disease can be entirely internal. This means that you will not witness any of the symptoms we have discussed so far. If your betta dies, and there is seemingly no other reason that you can see for this, there is a small chance they had an internal case of columnaris.

You can also look to a betta which is constantly rubbing itself against tank ornaments or whatever you have for the bottom of your tank. It is also very possible that if your betta has discomfort/infection around its mouth area, it isn’t going to be eating. A diminished appetite is definitely something to look for.

How Can I Treat Columnaris Betta?

Going through some of the worst offenders for betta fish diseases columnaris, we can see that many of them are preventable on your end. This extends to making sure your tank is cleaned and well-maintained at all times. Giving your betta a good diet is also a sure way to keep them fostering favorable infection conditions.

Checking on their stress levels, and making sure new fish are always quarantined after being brought home, are all great ways to lower the possibility of ever having to worry about any of this.

Even so, the infection can still occur, even under the best of circumstances. Understanding this can go a long way towards making sure you are ready with treatment options. You will want to start by quarantining any bettas or other fish you are certain have the infection.

Lowering the temperature by a couple of degrees can also be beneficial to a betta fighting the infection.

Furan-2 is one of the most popular treatment methods for betta fish with columnaris, you should also add aquarium salt as well as using Furan 2. 

Kanamycin is another popular antibiotic which can treat them. There are also medicated fish food options which can prove to be effective. Look for anything that contains Oxytetracycline.

What Is The Best Way To Prevent Cotton Wool Disease?

At the end of the day, your best bet for dealing with Columnaris outbreaks is to prevent it entirely. The tips we mentioned above will prove enormously useful. There are also vaccination options which you can explore.

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Jeff Colt

Jeff Colt

Hello, I'm Jeff- an aquarium enthusiast with over 25 years of experience caring for a wide array of tropical fish, including koi, goldfish bettas, cichlids and more! For me: Aquariums are like jello - there's always room for more!

4 thoughts on “Columnaris Betta (Cotton Wool Disease Symptoms&Treatment)”

  1. I’m not sure if my betta Phin has this. I have not been very good about changing the water regularly so today I did a full water change. I emptied all the old water out and replaced it with entirely new water from my faucet. I didn’t let the water sit out for long but I made sure it wasn’t freezing and made it so it felt room temperature. Ever since I put Phin back in his tank he has stuck his head in the pebbles at the bottom and hasn’t moved or eaten in hours. I also noticed that he has white, mold-like fuzz on the edge of his tail. It might have been there for more then just today and I hadn’t noticed it because of his dirty water, but I’m not sure. Please advice, I’m really worried about him, he has never acted this way before.

    • I am not recommending you have go treating for your betta if you’re unsure if he has it or not as these medications are harsh for any fish.

  2. Just lost my betta Lucifer to this disease, but it seems like it was just secondary. Looks like he had some internal issues before. Had to put him down. Heartbroken,but better to see him being painfree and dead than suffering. I honestly do not know what else it was, I kept changing the water frequently and checked on him all the time. Really sad now… Was my first fish. Got some shrimp and snail now, will get another thank for bettas or a bigger 1 for all of them.


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