Fin rot betta

Fin rot betta DEFAULT

Fin rot is a bacterial infection that commonly affects betta fish. This infection eats away at a betta’s beautiful fins and tail, causing them to look ragged and discolored.

While the effects of fin rot are small at first, if left untreated, the infection will get progressively worse until your betta dies.

Fortunately, there are multiple ways that you can cure and treat fin rot so that your betta makes a full recovery.

We will talk you through everything you need to know and help you to return your betta back to full health.

What Is Fin Rot?

betta fish fin rot
Fin rot is an infection characterized by ragged, deteriorating, discolored fins and caused by gram-negative bacteria (Pseudomonas fluorescens) or fungal pathogens. Your fish can become afflicted with fin rot due to poor water quality or a weakened immune system.

Your fish may have a weakened immune system for any number of reasons, including stress, irresponsible breeding practices, prior illness, injury, or inadequate water conditions.

If your fish gets fin rot, its fins will start to rot away, potentially deteriorating until it has no fins left. If left untreated, fin rot will eventually lead to the death of your fish.

Fin rot can be a problem for any fish (marine or freshwater), but bettas are particularly susceptible because their fins are so large and long. Ironically, this makes the problem more noticeable, so you should be able to spot it quickly and have a good chance of saving your betta.

While it can cause a lot of damage to your betta, fin rot is both treatable and preventable, so your fish is not doomed.

Is Fin Rot Contagious?

As a bacterial disease, fin rot is technically contagious, as the bacteria will multiply and can move to new fish through close contact.

However, if your betta’s tank mates have a strong immune system, they should be safe.

If you notice several of your fish getting fin rot at the same time, you likely have an issue in your tank that’s negatively affecting the immune systems of all your fish, such as poor water quality or conditions.


Fin rot is a disease that gets progressively worse over time. If it is left to run its course, your betta will eventually die. Luckily, the symptoms are quite conspicuous, so you should notice them early.

Symptoms of fin rot are most apparent on the tail fin, but the infection can affect any fin.

Initially, the infection will manifest itself as a thin white border on one of the fish’s fins. This white border may not necessarily stand out, depending on the color of the fish and its environment.

Over time, the white border will start getting thicker and more visible. It may darken in color too, somewhere from grey to brown to black, but it could remain white.

The colored area marks the infected area. As the border thickens, the bits on the edge will begin to fall away, shortening the fin and making it look frayed.

This could continue until the entire fin has been eaten away, making swimming incredibly difficult on your betta.

Once the fin is completely gone, the rotting can continue and start eating away at the body where the affected fin had been attached, causing inflammation.

Throughout the process, you may observe your betta behaving differently too.

A fish’s immune system has to work very hard when fighting off disease. This uses up a lot of energy, leaving them weak and fatigued.

To make the issue worse, fish affected with fin rot often lose their appetite and stop eating, so they receive less energy from their diet.

Your betta will likely begin to stay away from tank mates and might spend a lot of its time laying on the substrate to rest.

If you watch your fish regularly, you should be able to spot fin rot on your betta quite quickly. Their long flowing fins make deterioration and color change quite noticeable.

Fin rot is harder to spot on smaller fish until further symptoms arise.


Usually, a pathogen needs to be introduced to an aquarium before a certain disease arises, perhaps when adding new fish or decorations.

However, the bacteria and pathogens that cause fin rot can often be found in aquariums without your fish having developed cases.

There are two possible types of pathogens that could cause the fin rot on your betta: the gram-negative bacteria called Pseudomonas fluorescens and a fungal pathogen.

These usually only become an issue if the immune system of your betta weakens, as it will be unable to fight them off effectively.

Poor Water Conditions

A weakened immune system is most often caused by poor water conditions in the aquarium.

Perhaps the temperature of the water has changed over a hot summer, or maybe there are too much feces in the tank due to overcrowding.

Whatever the reason for the poor conditions, you should be able to identify using a water testing kit and a thermometer, so you can then fix it.

Poor Diet

Another reason for a weakened immune system is a poor diet. You may not be feeding your betta enough, or it may not be receiving all of the nutrients it needs to stay healthy.

Is their diet composed solely of dried foods? This could be a problem because most of the nutrients are lost during manufacturing. Live or frozen foods are nutrient-rich, making them much better options.

A varied diet is an ideal one. This ensures that your betta will receive a wide range of nutrients.

Other Health Problems

Having one health problem leaves your betta more susceptible to developing more.

You might not have noticed that your betta had contracted another disease before fin rot. Fighting a disease uses energy, leaving them exposed to others.

Physical injuries make it easier for a pathogen to affect a fish because the wound offers another entry point to the body. Bettas are known to fight from time to time, so injuries can happen more often.

Bettas are a prime target for fin-nipping fish due to their long fins. This can easily lead to fin rot too.


A stressed fish will be less able to fight off disease. While the previous potential causes will result in stress, there are some more generic reasons for stress too.

Maybe there is a tank mate that keeps harassing your betta. It would be even worse if the tank mate were a fin-nipper since injuries make the disease more likely.

Bettas are well able to look after themselves, but fighting with tank mates uses up a lot of energy and stresses them out.

Bright lights can stress your betta, especially if they have nowhere shaded that they can go to hide.

Treating Fin Rot

There are ways to treat fin rot of different stages and severities. The important thing is to start treatment as soon as possible to give your betta the best chance of survival.

If you can, set up a quarantine tank. This will help to prevent the spread of disease to other fish. It also protects the tank mates from any effects that the treatment may cause them.


Treatments are unlikely to be ineffective if the underlying problem (e.g. poor water quality) is still occurring.

Before starting treatment, you need to diagnose what caused the fin rot in the first place. Once you have identified what the cause is, you can fix it and start treatment.

Check the temperature and use a water testing kit to determine the levels of nitrite, nitrate, and ammonia in the aquarium.

If the conditions are not right, perform a water change and give the tank a good wipe down. Cleaning the tank like this is a good idea even if the conditions seem okay.

Think about what you are feeding your fish and if their diet is as healthy as it could be. Change their diet if you need to, though your betta may not accept it right away if it’s lacking an appetite.

You will need the perfect environment for your betta if you want it to recover. Once conditions are perfect, remove anything that causes stress, such as boisterous tank mates.

Depending on the treatment, separating your betta is usually a good idea anyway, to avoid the treatment affecting the rest of your fish.

Diagnosing and fixing the initial problem can sometimes be enough to help your betta fight off the disease, without the need for further treatment.

Treating Mild Fin Rot

You can choose a treatment based on how advanced the fin rot is.

Mild fin rot will have arisen recently, so the fin tips will have started to change color and possibly started fraying as the first few pieces fall away.

Treating mild fin rot involves adding freshwater aquarium salt to the water (not table salt). This can be found in most pet stores.

The aquarium salt helps to heal wounds and reduce stress. It will damage your live plants though, so make sure there aren’t any in the tank.

Add one teaspoon of aquarium salt for each gallon of water in the aquarium. Pre-mix the salt in the water before adding it to the tank since the raw salt can hurt your betta.

Perform a 90% water change every day, treating the new water with the appropriate amount of salt each time.

The amount of salt you need to add may vary depending on the brand you purchase, so read the packaging carefully before the first dose.

Do not use this treatment for longer than 10 days. Prolonged exposure to salt can poison your betta and damage their kidneys.

If there has been no positive effect after 10 days, try the next treatment.

Treating Advanced Fin Rot

Advanced fin rot will likely have been a problem for a bit longer. Large portions of the fins will have started to fall away.

Treating advanced fin rot involves using medications.

Some medications can lower the oxygen content of the water, so it is worth adding an air stone to your quarantine tank.

If you are using a filter with carbon, remove the carbon as it can strip the medication from the water.

Follow the dosing instructions on the medication you have purchased.

Before each treatment, perform a large water change to avoid overdosing. Hopefully, you will see some improvements after a week or two. Once treatment is complete, you can return your betta to its regular aquarium.

Any new growth that develops on their fin will be delicate, so mate sure their environment is calm and without any boisterous tank mates. Sharp decorations should be avoided too.

How Do you Know if Fin Rot Is Cured?

Treatments can take a few days or even weeks to be effective, so do not be disheartened if your betta does not show any immediate improvements.

Rather than looking for improvements, look for any signs that the infection is getting worse. If the fin is no longer deteriorating and is staying a consistent size, then you will likely see improvements soon.

You will eventually spot some regrowth of the fin as the dead parts are replaced. This should be coupled with some healthier-looking colors.

You should see some improvements in their behavior too. Hopefully, their appetite will improve, so they can begin to feed like normal. This will increase their energy levels so they can move around the aquarium more easily.

Keep a close eye on your betta. You should be able to judge when its fins and behavior have returned to normal.

Preventing Fin Rot

If you have never experienced fin rot in your aquarium, or you don’t want it to happen again, taking preventative measures will help you to avoid the anxiety of potentially losing your fish in the future.

Before even starting your aquarium, there are steps you can take to reduce the chance of disease.

Try to get the largest tank that you can. It is much easier for pollutants to build up quickly in a smaller volume of water, so it is harder to maintain the perfect conditions.

Think carefully about the bioload that your tank and filtration system can handle. Overcrowding the tank will produce too much waste and lower the quality of the water, not to mention stress on your fish.

Once the aquarium is up and running, having a regular tank cleaning routine is the best thing you can do to prevent fin rot.

Diseases thrive in poor water conditions, so don’t give them the opportunity.

A clean tank will help to keep your betta’s immune system strong, as will a healthy and nutritious diet.

Whenever you are watching your betta, look carefully at their fins for signs of a color change. Observing your fish regularly will help you to spot disease as quickly as possible.

The sooner you find the disease, the quicker and more effective treatment should be.

Buying Your Betta

Be vigilant when buying your betta and check that it does not already have fin rot. The disease can be common in pet stores depending on their quality of care.

Look over the betta that you intend to purchase. A deteriorating tail or loss of color on the fin tips are good indicators that the fish has fin rot. These should be easy to spot.

Take this time to look for signs of other diseases too, such as the white spots associated with ich, or even just physical injuries.

If you notice anything out of the ordinary, the safest option is to shop elsewhere. Buying a healthy betta is crucial to it surviving the transition into your aquarium.


If your betta is experiencing fin rot, it is easy to panic and think that the worst will happen.

Take a step back to figure out what has caused the problem. You can then fix this and move on to treating your fish in a quarantine tank.

There are a couple of methods for you to choose from, each is useful for different stages of fin rot. If one does not work, you have the other to fall back on.

Once your betta is back to full health, you can return it to your main aquarium and take preventative measures to reduce the chance of fin rot making a return.

It is important to remind yourself that fin rot is a common disease that many people encounter, so you are not a bad aquarist if it develops in your tank.

Whatever the cause, start treating your betta as soon as possible and it should be fine.

Have you experienced fin rot before? Let us know what happened in the comments below…


Treating Stubburn Fin Rot in Betta Fish

Shelbi with Fin Rot. Image provided by BS
Q: BS wrote,

My betta fish Shelbi has fin rot now. His water is and has been pristine with the parameters at their perfect spots. He had blackened tips when I bought him but I thought it was just his coloring. Now his fin tips are damaged and broken. I did water changes and checked his water repeatedly before getting medications to see if he could heal himself but he just got worse and I didn’t want to waste time while his tail dissolved away. I kept him in unmedicated, clean water for a month and a half. When it just kept getting worse, I went to the pet store and bought T.C. Tetracycline and Maracyn-Two. My other fish, Ember had gotten fin rot now, too because I didn’t have another tank to separate him from Shelbi. Ember cleared up almost immediately and I bought a hospital tank for Shelbi. Shelbi has gone through two Tetracycline treatments to no avail. I started Maracyn-Two yesterday and no improvement yet. What else can I do? I have attached a couple pictures of his fin rot. Will his tail grow back the same as it was? Right now it looks very tattered and short and the fin rot is progressing, fast. How long does it take to grow back and regain color?

Also, I went out of town for a week and when I came back, Shelbi had a white speck on him. (it’s actually not really white, it’s kind of gray). It’s not protruding or clumpy or anything, just a white speck, so I don’t think it’s ich. I have also attached a picture of it. What do you think it is?

Poor Shelbi has had a rough time lately, I am trying to do my best to take care of him!

His hospital tank is:
-10 gallons
-heated to 79 degrees
-medium sized gravel
-silk plants and cave
-I clean it once a week
-all perimeters are right

Thank you so much for all of the help you have given me with Ember and Shelbi. It has been so great to have someone like you to go to with questions for a reliable answer.

A: Wow, that Shelbi is one beautiful fish. I just love his color.

Fin rot, while not typically life threatening, is still a very tricky illness because it can take a long time to overcome. Torn fins or fins that have been nipped by another fish tend to regrow quickly once the problem has been addressed. Usually within a few days new tissue growth can be seen and significant regrowth can be observed within a few weeks. Fin rot, however, is different as it is characterized as fin tissue loss due to a bacterial infection. It is not uncommon for the regrowth to be much slower or for multiple relapses to occur once new tissue has begun to take hold. Some betta keepers battle fin rot for months before they get a good handle on it.

When the fins do regrow, you may notice some slight differences in color (usually minor) or you could see a curling of the rays, especially in crowntails. This curl is usually permanent and while it may not win any awards for your fish, it will not affect him in any other way.

Fortunately, based on your photos, Shelbi’s fin rot is very minor and your hospital tank set up seems like a good healing environment. You may find, once he is finished with this course of antibiotics, that you can continue to monitor him in his usual aquarium.

Things to watch out for while he is mending:
1. Any ammonia or nitrite in the water
2. Fluctuating pH
3. Organic debris collecting where the fish may drag his tail
4. Water that is too cool or fluctuates greatly
5. Tank décor or other fish that may tear his fragile fins

If you find that his fin rot continues to worsen you may need to dig a little deeper into the cause. For example, how is your tap water treated? Are you using a water conditioner that neutralizes chloramines and heavy metals as well as chlorine? Are there other stressors that could be creating a hazard? What is your pH level from the tap as well as in the aquarium? If it is fluctuating, have you tested your carbonate hardness (KH)? It might be that we just need to take a closer look at some of the other water parameters.

You can always email me the results of your water tests and I can look them over too to see if there is anything unusual or missing from your test regimen. Let us know how he is doing. Hopefully he is responding to the Maracyn-Two treatment.

The white spec is another story. It is really difficult for me to see what is going on there. It could be the early signs of a fungus-looking bacterial infection or an actual fungus. I did see a case recently where the betta was loosing pigment and his scales around his head were turning white (not raised or fuzzy). It wasn’t anything I had seen before but would be curious if you think it is the same thing. Does it look like the scales themselves are changing color or falling out?



Filed Under: Betta splendens, Fin Rot, Illness & DiseaseTagged With: betta, betta aquarium, betta diseases, betta fish, betta tankmates, bettas, healthy betta

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How to Identify and Treat Betta Fin Rot - Pin

Having a pet betta is a ton of fun, but the downside to these colorful fellows is that they are prone to health problems. The most common ailment you’ll typically see is known as Betta Fin Rot. It’s also called Fin Melt, Tail Rot, and even Body Rot, depending on how far the disease advances before you get it under control.

Did you know that using aquarium salts is one of the best interventions for treating betta fin and tail rot? Discover everything you need to know about identifying, treating, and preventing this painful and common disease in bettas.

A Guide to Betta Fin and Body Rot

We love our betta fish for their scrappy personalities and elaborate rainbow-hued fins. Those beautiful, long tail fins come with a downside, however. They make it more likely that your betta will develop a disease known as fin rot.

If you own bettas, chances are you’ll run into fin problems eventually. Every betta owner should learn how to identify and cure it in its earliest stages, so your fish has the best chance for a full recovery. You also need to know which measures to take to prevent further outbreaks from occurring.

What is Fin Rot?

Image of a betta fish in a tank with obvious fin rot

Fin rot is a progressive disease that eats away at and dissolves the delicate tissues of your betta’s fins and tail. If it isn’t treated promptly, it will advance to your fish’s body, where it eats into the scales and causes open, gaping sores to form. Even with treatment, severe cases may be fatal to your betta.

Fin Rot vs Fin Loss—What’s the difference?

In the earliest stages, it can be difficult to tell fin rot from an injury to your betta’s tail or other fins. Varieties with especially elaborate tail or pectoral fins, like the double-tailed and elephant ear bettas, often damage their fancy fins accidentally on your tank decor or get nipped by other fish in the aquarium.

These varieties are also more likely to self-harm if their tank’s conditions are out of their ideal range. The good news is that the treatment for generalized fin loss and an early case of fin rot are the same. If you notice any damage to your betta’s fins, it’s best to treat it as a mild case to prevent the problem from getting worse.

What Causes Fin Rot and Why Are Bettas Prone to it?

Betta fish are prone to this disease because they have those long, fancy tails. Female bettas and varieties with shorter fins, like the plakat, rarely develop fin or tail rot. It’s the price fancy male bettas pay for having such flashy and elaborate fins.

Fight fish close up

There are a few reasons why a betta might develop fin rot. The problem is usually caused by an underlying bacterial or fungal infection that your fish has picked up. But why does it just appear suddenly, seemingly out of nowhere?

Stress is usually the root or ultimate cause. It’s normal for an aquarium to have colonies of bacteria and even fungi present in the water. A healthy fish usually has no problems coexisting with these organisms. But when your fish is stressed, their immune system crashes and allows the infection to run wild.

Symptoms and Diagnosing Your Sick Betta

How can you tell if your betta is getting sick? The first signs are usually very non-specific and mild. Your betta may be under stress or getting sick if:

  • Their appetite decreases or they refuse to eat.
  • Their overall color is unusually dull and pale.
  • The betta fish fins look rippled or are curling up along the edges.
  • They are picking at their own fins or rubbing their fins and/or body along the substrate or aquarium decor.
Siamese fighting fish isolated on black background.

If you notice any of these signs of stress, you should check your tank and see if you can identify any problems with your set-up. If your betta is developing fin rot, you may be able to halt its progression before they show more obvious signs of the disease.

Stages—Details on Symptoms and Diagnosis

What does betta fin rot look like, and what happens if you get the diagnosis wrong? The changes recommended for mild cases often cure other problems as well, so a specific diagnosis may not be needed. Once things progress to moderate or severe, it’s usually obvious that fin rot is what you’re dealing with.

Treating Your Betta for Fin Rot

What should you do once you’ve diagnosed your betta with fin rot? The first thing you should do is check your aquarium set-up and see if you can identify the reason for the illness. It doesn’t make sense to treat your betta until you’ve fixed the underlying problem in your tank, and for mild cases that could be all the cure you need!

Identify and Fix Any Problems With Your Aquarium Set-Up

Remember, the microorganisms behind fin and body rot are nearly always present in your aquarium water. If your betta develops signs of fin rot, there’s likely a reason why their immune system suddenly shut down and made them vulnerable to infection.

The most common reason for a betta to get sick is from stress, and the most common reason for a stressed betta is inadequate or poor water conditions. If you’re having problems with the conditions in your betta aquarium the reasons could be:

Fish tank decoration, detail of a room to rest
  • Water temperature is outside the ideal range of 75°F to 86°F.
  • Water temperature fluctuates more than a few degrees over a 24-hour period.
  • No heater in your betta tank.
  • Water changes are infrequent or not done on an appropriate schedule.
  • The tank is too small for your betta (under the recommended 5-gallons).
  • The tank is overcrowded with plants and decor.
  • There’s too many other fish or aquatic species in the tank with your betta.

Treating Cases of Mild Fin Rot

Once you’ve looked over your set-up, you’ll probably have a good idea about the possible cause or causes of your betta’s infection.

If you correct the problem by adding a heater, reducing the number of decorations or tank mates and/or increasing the frequency of water changes, your betta may recover without needing further treatments.

Your fish should bounce back fairly quickly from a mild case of fin rot. If your betta does not show improvement within two weeks after you’ve made these changes to your aquarium, or if the disease progresses further, you’ll have to take more drastic measures to treat them. You might even need to use a hospital tank.

Using a Hospital or Quarantine Tank

Beautiful siamese betta fish in the glass and water at wall wooden shelf

It’s always a good idea to keep a spare tank on hand in case you need to isolate a sick fish for treatment. A hospital tank is usually a small 2 to 5-gallon set-up with no decorations and a basic sponge filter and heater. I don’t even add substrate to my quarantine tanks, and leave them bare instead.

Why do aquarists use hospital tanks? The problem with treating a sick betta in a community tank is that the cure may be toxic and stressful in and of itself. Many medications kill live plants and are fatal to certain aquatic species. Sometimes, you just can’t treat the entire tank for practical reasons.

Using a hospital tank to isolate your sick betta makes it easier to do frequent water changes. Even if you only have a single betta, it may be better to deal with a hospital tank for treatment than your usual 10-gallon set-up. You should always use a 1-stage filter in these tanks since meds can reduce the amount of oxygen the water carries.

How to Treat Moderate Fin Rot

If you’ve made changes to your tank and improved the water conditions, but the fin rot is still progressing, you’ll need to take the next step. One of the best treatments for fin rot is to simply add aquarium salts to your tank!

API Aquarium Salt, Promotes Fish Health and Disease Recovery in Freshwater Aquariums, Use When Changing Water, When Setting up a New Freshwater Aquarium and When Treating Fish Disease

Of course, there’s more to this than just sprinkling salt in your tank. Used improperly, aquarium salts can burn your betta, and they are lethal to most live plants. The salts are also toxic to your betta, and may eventually cause kidney or liver damage. You should only treat your betta with aquarium salts for 10 days at a time.

You’ll have to mix the salt-and-water solution in a bucket first and add it to the hospital tank before you acclimate your betta to the new set-up. If you are dosing a community tank rather than using a hospital set-up, be sure the other animals can handle the salt at that concentration.

To treat your betta’s fin rot with aquarium salts:

  • Follow the directions on the container to mix the appropriate strength solution for betta fish, remembering to add a water conditioner to remove any chlorine from your tap.
    • Move your tank or hospital set-up to an area where the temperature does not normally exceed 78°F. Higher temperatures can encourage the infection to spread.
    • Fill your hospital tank with the saltwater solution and add the heater and sponge filter.
    • Set the heater to maintain the temperature at 78°F and wait until the temperature is stable before introducing your betta.
  • Slowly acclimate your betta to the hospital tank, just as you would when adding a new fish to an aquarium.

During the 10-day saltwater treatment:

Applying salt treatment to aquarium water.
  • Change out 50% of the water in the tank every day, adding back the same amount of pre-mixed saltwater solution.
    • The water needs to be at the same temperature as your aquarium when you add it to your hospital tank.
  • Be sure the salt concentration remains the same regardless of how much water you change, or you might overdose your fish.
    • For example: If you used 1 tablespoon (3 teaspoons) of aquarium salts to mix 5 gallons of water initially for your hospital tank, then you should mix 1.5 teaspoons of salt to 2.5 gallons of water to create the same concentration for a 50% water change.
  • It’s best to only mix as much saltwater solution as you need for a single water change, rather than making a large batch and storing it for later use.
    • As the water evaporates, it leaves the salt behind. Over a few days, the concentration of salt in the solution will increase as the water level drops, which could poison your betta.
  • Monitor your betta’s appetite and look for signs of improvement. While your betta is being treated, clean your primary aquarium well and rinse the substrate, decorations, and any live plants before adding fresh tap water and restarting the tank.

Treatment for Severe Fin Rot

API Fungus Cure Freshwater Fish Powder Medication 10-Count Box

If your betta doesn’t improve while using the aquarium salts, or if you didn’t notice the disease until it progressed to a severe level, you’ll need to take the next step in treatment. This means you’ll have to use medications in your aquarium. If your betta has other infections from their lowered immune system the meds will cure those too.

Just as with moderate cases, it’s best to use a hospital tank when medicating your betta for severe fin or tail rot. I usually start by medicating with an antibiotic such as Maracyn II or API Fungus Cure, which also tackles secondary bacterial infections.

Follow the instructions on the package and finish the course of treatment even if your fish improves quickly. The length of time will vary depending on the medication you use. You may have to do several rounds of treatment to cure your betta’s fin rot:

  • Maintain your aquarium at 78°F to reduce the activity of the bacteria.
  • Do water changes as directed by the packaging and be sure to add the appropriate amount of medication after water changes to keep the dose of medication consistent.
  • A sponge filter or 1-stage filter is a must when using medications in your tank, but be sure there’s no media in the filter or it will remove the meds from the water.

Frequently Asked Questions

There are a few questions that always come up when someone’s dealing with a case of fin rot. The most common questions I’ve been asked include:

Q: How Can I Tell if My Betta is Getting Better?

A: It depends on how long you betta’s been sick and how severe their disease is, but you’ll quickly notice your betta’s getting better if you’re using the right treatment. Within a day or so they should look a bit brighter and be more active. If they’ve been off their food, you should notice that their appetite improves too.

Within a week, the damaged edges of your betta’s fins should start to develop a clear film as they heal. The discolored edges of the fins should disappear and return to their normal color. Any other areas of abnormal red, black or white colorations on the fins or body should disappear as well.

Q: Will My Betta’s Fins Grow Back?

A: Bettas with mild or moderate cases of fin rot usually fully recover, although it can take a few weeks for their tail or fins to regrow. Similar to human fingernails, betta’s fins typically grow a few millimeters a month.

Aquarian fish swims in aquarium water

Bettas with severe cases of fin rot may never return to their original appearance, even if they survive the infection and treatment protocol. If your betta lost a substantial part of their fins, the damage may be too extensive and the scarring permanent.

Q: Is Fin Rot Contagious?

A: This one is tricky because the answer is both yes and no. Since the bacteria and/or fungi that lead to fin rot are usually present in your aquarium, any animal in the tank is potentially susceptible to infection. But most healthy animals do not get sick, even when there are pathogens in the water.

If your betta develops fin rot, there’s probably something else wrong with your tank that made your fish susceptible to infection. Obviously, other animals in the tank experience the same conditions and could also get sick. That’s why it’s best to identify and fix the tank’s problem and then treat your sick fish for the infection.

Q: Can Fin Rot Kill My Betta Fish?

A: Yes, many bettas with severe fin rot do not survive the infection. If you delay treatment until your fish develops body rot they are unlikely to recover. The medications used for treatment are toxic and also cause stress to your betta. A betta with a severe infection may not be strong enough to survive the treatment.

Purple betta fish in aquarium.

The good news is that fin rot is highly treatable in the mild-to-moderate stages, so if you catch things early your betta has an excellent chance of a full recovery!

Q: How Can I Prevent My Betta From Getting Fin Rot?

A: There’s an old saying that “an ounce of prevention is worth a pound of cure,” and that’s a great way to think about it. While you can’t completely eliminate bacteria or fungi from your tank, you can ensure that your fish stays healthy so they are unlikely to develop an infection.

The key to preventing fin rot and maintaining a healthy betta is to:

Asian women set the fish tank
  • Keep them in a roomy tank (5-gallons and up).
  • Don’t crowd them with too many decorations or tank mates.
  • Use a heater to maintain its ideal temperature range (75°F to 86°F).
  • Stick to a regular schedule for filter maintenance and water changes.
  • Don’t over or underfeed your betta.


Fin disease is a common problem in betta fish with long fancy tails, but it’s highly treatable if you catch the infection early. Once the infection advances to body rot, a betta’s chance of survival is low. Simply making some small changes to your aquarium set-up can dramatically reduce your betta’s likelihood of infection.

Low or inconsistent aquarium temperatures and infrequent water changes are the leading cause of this disease. Most betta owners will experience rot at some point, so you need to know the symptoms and how to cure it. The faster you fix the problem and treat your fish, the better chance your betta will completely recover!

Betta Finrot Infographic
Jen Clifford

Jen has more than 30 years experience as a biologist, aquarist, and fishkeeper. She is an expert in setting up new tanks and maintaining naturally-planted freshwater habitats, and has experience raising a wide variety of aquatic species.


Betta Fish Fin Rot: Symptoms, Causes, and Treatments

One of the worst things a betta fish owner can witness happening to their betta’s beautiful long fins is to watch pieces of it waste away. This tragic illness is known as fin rot. Just as the name implies, the fin begins to rot away in small amounts over a short period. Fin rot is common amongst all types of betta fish and can easily be cured with the right medication and care.

If you notice that your bettas tail is not looking how it used to, this article can help you!

Table of contents

Fin Rot Explained

Fin rot is caused by an infection that slowly begins to eat away at bettas fins. This results in the fins looking ragged and torn. It will appear as if your betta’s fins have been through a blender. This is usually caused by a gram-negative bacteria or fungal infection which is prevalent in betta fish species. The fins also begin to melt, and it will seem like bits of the fins are fading away which leaves uneven and ragged fins. Every betta owner will deal with this illness sometime in their life and luckily it has a high success rate and most healthy bettas can easily overcome this illness.

Tail Biting or Fin Rot?

Both tail biting and fin rot look identical, however, they are truthfully quite different. Both in terms of treatment and causes.

For one, tail biting is a self-destructive behavior brought on by stress and boredom in bettas. Whereas fin rot is controlled by pathogens that eat away at fins without the betta’s involvement.

These two issues are equally serious, but treatment varies. For instance, stress that leads to tail biting should be addressed by finding the root of the issue, whether it is caused by a small tank or more commonly strong flowing filters. Many people will witness their betta biting their tail and see bite-sized marks towards the ends of the fins which makes it easy to diagnose. Tail biting can make the fins more susceptible to bacteria and fungus that can cause a form of fin rot.

Sometimes incompatible tank mats will nip the fins of your betta which can give them a ragged appearance. Always monitor the behavior of certain fish if you add them into your betta’s tank.


close up betta fish

Determining if your betta has fin rot is the first step to a successful treatment. Keep in mind your betta may not show all the symptoms, but if you notice most of the symptoms are showing up on your betta fish, then it is likely they are suffering from either a mild or severe case of fin rot.

  • Ragged fins
  • Holes in fins
  • Tears
  • Dangling pieces of tail flesh
  • Lethargy
  • Bottom sitting
  • Loss of appetite
  • Necrosis of the dead skin
  • White film at the ends of the fins (new growth)
  • Visible blood vessels

5 Causes of Fin Rot in Bettas

  • Bacterial infection: This is the most common cause of fin rot and is from a gram-negative bacterium that is present in the water column. This bacterium can enter the smallest wound on a betta and become severe if not treated properly.
  • Fungal infection: This is a less common reason that causes fin rot, but the white fluffy growths acquainted by a fungus infection can cause a mild case of fin melting that mimics fin rot symptoms.
  • Dirty water: It is no surprise that dirty water hosts a variety of disease-causing bacteria. If your tank is dirty and cloudy with regular algae blooms, then your betta is susceptible to bacteria that will eat away at their fins. Bettas need a filter and a fully cycled tank. Regular water changes should also be done to keep the tank clean.
  • Small aquaria: Small tanks cause stress and allow the water to rapidly become toxic from high levels of ammonia from fish waste. Bowls, vases, and tanks under 5 gallons are unsuitable for bettas and can quickly poison a fish in its waste. Fin melting is common from the burns sustained from the toxins in the water.
  • Physical damage: Bettas can sustain injuries from rough decorations and fake plants, as well as getting stuck in a filter or as a result from fin nipping.

Effective Treatments for fin rot

These medications seem to have the best healing ability for a betta with fin rot. There are two stages to treatment that contain different medications. Here is a thorough treatment list to help your betta successfully heal from their ailments.

Preventing Fin Rot in Bettas

Fin rot can easily be prevented by providing your betta fish with the right conditions. Bettas should be kept in a fully cycled tank (established beneficial bacteria from the nitrogen cycle) that is over 5 gallons. Although a 10 to 20 gallon is better long-term. The tank should have a filter and heater to keep the water ideal. A 30% water change should be done weekly to remove toxins that build up in the water. You can also place 1% of aquarium salt in the water to promote your betta’s slime coat naturally.

Another medication can be placed in the water to keep the overall water clean and free of harmful bacteria and fungus. Bettas should only have live or silicone plants in their tank to prevent rough decorations from snagging and tearing their fins. Always make sure the filter is not strong enough to suck in your betta as they are generally quite poor swimmers.


A healthy betta can easily withstand major symptoms associated with fin rot and survive treatment and the healing process. Bettas are quite hardy and should rarely fall ill if they are fed a good diet, have an appropriate tank with the necessary equipment, and on top of all that have their water changed regularly to keep the ammonia and nitrate down.

We hope this article has helped you to diagnose, treat and prevent fin rot in your betta fish!

Featured Image Credit: SoReaux, Shutterstock

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Betta fin rot

Treating fin rot

Treating fin rot

What causes fin rot?

Betta fish fin rot, like many fish diseases, is caused by a combination of factors. It’s a bacterial or fungal infection, meaning the “melting” is caused by bacteria or fungus eating away at the fins. Bacteria such as Pseudomonas that cause fin rot are not that dangerous for your fish by themselves and can actually be found in any aquarium. The real danger is secondary infection, such as when the fish rips its (tail) fin or is otherwise injured, for example by other fish. The bacteria and fungus can easily latch onto the open wound and cause it to become infected.

Another huge factor in fin rot is stress. A stressed fish is much more susceptible to any disease and especially fin rot! Stress can be caused by many things, but the main reasons for fin rot are bad water quality and an improperly cycled aquarium caused by overstocking or lack of water changes. Insufficient feeding, bad choice of tankmates, injuries, disease or stress from transport and all other things that cause stress and/or injuries to a fish increase the chances of infection. The oranda below has both dropsy and a case of fin rot on the pelvic fins.


Siamese fighting fish

Preventing fin rot

There are a few simple steps you can take to stop fin rot before it has a chance to start.

– Keep your aquarium clean and ammonia and nitrite values at zero at all times. Make sure the tank is properly cycled before you introduce any fish.

– Research the fish you’re interested in and their needs and compatibility to prevent aggression and overstocking. Although it’s tempting to buy as many fish as possible, a slightly understocked aquarium is much less stressful for both you (less maintenance) and the fish!

– Once everything is up and running and the fish/invertebrates are introduced, do plenty of water changes according to your stocking level and the bioload of your fish, making sure to dechlorinate the water with a dechlorinator like Prime unless you live in a country that doesn’t use chlorine/chloramine in tap water.

– Feed a varied diet of high quality food and prevent over- or underfeeding.

– Avoid commercially bred very long finned fish such as veiltail goldfish or angelfish, halfmoon bettas and especially rosetail bettas. The large fins are easily damaged and bettas may actually bite off excessive finnage, leaving an open wound.

These steps will not prevent all cases of fin rot but if you always make sure to keep the stress levels of your fish as low as possible and try to prevent any damage/injury, the chances of infection are severely reduced.


Diagnosing fin rot

Fin rot is not difficult to diagnose. In the earliest stage, the fins may get red and inflamed looking streaks. This is not visible in all fish though! When the infection progresses, the typical “melting” of the fins begins. In severe cases and with long finned fish, this can happen very quickly, with entire pieces of the fins falling off. The fish may become lethargic and the fins will be left looking ragged and with white or dark-colored edges depending on the type of infection.

In very severe cases the fins can be eaten away completely. When this happens and the infection reaches the body it’s usually too late to save the fish, so it’s vital to act quickly when you see any of these symptoms.


Betta fish

Curing fin rot

In very early cases, increasing water changes and keeping the aquarium extra clean may be enough to stop fin rot. If the infection is already getting serious, it’s a better idea to start treatment right away. Fish that are in a community aquarium should be quarantined for this, as you don’t want to expose healthy fish to unnecessary medication. Keep the quarantine water very clean to prevent further deterioration of the fins. For more information about quarantining fish.

If clean water isn’t working or the fin rot is already too severe, it’s unfortunately time to move on to stronger medication: antibiotics. These are not available over the counter everywhere, but in the US you should be able to find them. Maracyn 2 treats gram-negative bacteria that are usually the cause of fin rot and is a popular treatment for bacterial fish disease. With the right treatment you should see some fin regrowth in no time. The bettas pictured below are the same fish!

Fin rot is one of the most easily prevented aquarium fish diseases. Although there’s always a chance you may end up with an infected fish after transport from the store, moving or an accident, keeping up with maintenance and doing research on proper aquarium care and tankmates should help you prevent almost all cases.

If you do spot fin rot on one of your fish, keep a very close eye on your water values and take the time to re-evaluate your water change schedule and the amount of fish you keep in the tank!

Photo by Mason

Fin rot is one of the most easily prevented aquarium fish diseases. Although there’s always a chance you may end up with an infected fish after transport from the store, moving or an accident, keeping up with maintenance and doing research on proper aquarium care and tankmates should help you prevent almost all cases.

If you do spot fin rot on one of your fish, keep a very close eye on your water values and take the time to re-evaluate your water change schedule and the amount of fish you keep in the tank!

If you have any more questions about preventing and treating fin rot or if you want to share your experience, feel free to leave a comment below. Happy!


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Fin rot

Fin rot is a symptom of disease or the actual disease in fish. This is a disease which is most often observed in aquaria and aquaculture, but can also occur in natural populations.[1]

Fin rot can be the result of a bacterial infection (Pseudomonas fluorescens, which causes a ragged rotting of the fin), or as a fungal infection (which rots the fin more evenly and is more likely to produce a white "edge"). Sometimes, both types of infection are seen together. Infection is commonly brought on by bad water conditions, injury, poor diet, stress, or as a secondary infection in a fish which is already stressed by other disease.

Fin rot starts at the edge of the fins, and destroys more and more tissue until it reaches the fin base. If it does reach the fin base, the fish will never be able to regenerate the lost tissue. At this point, the disease may begin to attack the fish's body; this is called advanced fin and body rot.

Fin rot is common in bettas due to poor water conditions in pet stores.


  • Fin edges turn black / brown
  • Fins fray
  • Base of fins inflamed
  • Entire fin may rot away or fall off in large chunks
  • Fins have white dots (if these are seen on the body it is possibly a symptom of Ichthyophthirius multifiliis)
Example of fins fraying on a male betta fish.


  • Change the water and check the filter
  • Treat with a suitable treatment such as phenoxyethanol, malachite green methylene blue or other proprietary agent (most seem to prefer aquarium salt; however, it is important to make sure the product is for freshwater, not saltwater, fish).[2]
  • Find out the pH and correct it if necessary.
  • Use antibiotics if the rotting is jagged.
  • Use antifungal medication if the rot is more evenly spread out and the fin has holes. This may also be a symptom of an external columnaris infection, especially if it progresses rapidly (within 24 hours) and the rotted edge has a white, fuzzy appearance.
  • Water temperature should be changed to 24–26 °C.


Fin rot can be prevented with good water quality, feeding fresh food in small portions and maintaining constant water temperature. Keeping the tank from becoming cluttered (for domestic fish) will also help prevent fin rot.


  1. ^"Ninth Flatfish Biology Conference"(PDF). December 1–2, 2004. p. 68. Retrieved 2012-10-13.
  2. ^Bailey, Mary; Burgess, Peter (1999). Tropical fishlopaedia : a complete guide to fish care. Lydney, Gloucestershire: Ringpress. ISBN .

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