Freshwater Fish

Betta Fish Fin Rot: Symptoms, Causes & Treatment

Owning a pet betta is a lot of fun, but the downside to these colorful types is that they are prone to health problems. The most common ailment you will typically see is known as Betta Fin Rot. It is also called Fin Melt, Tail Rot, and even Body Rot, depending on how far the disease progresses before it is controlled.

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

A GUIDE TO Betta Fish Fin Rot

We love our betta fish for their scrappy personalities and elaborate rainbow-colored fins. However, those beautiful long tail fins have a downside. They make it more likely that your betta fish will develop a disease known as fin rot.

If you own bettas, chances are you will eventually have fin problems. Every betta fish owner should learn how to identify and cure it in its early stages, so that your fish has the best chance of a full recovery. You also need to know what steps to take to prevent further outbreaks.


>Fin rot is a progressive disease that corrodes and dissolves the delicate fin and tail tissues of your betta fish. If not treated immediately, it will progress to your fish’s body, where it eats away at the scales and causes open, open sores to form. Even with treatment, severe cases can be fatal to your betta.


In the early stages, it can be difficult to distinguish fin rot from an injury to your betta fish ‘s tail or other fins. Varieties with specially elaborated tail or pectoral fins, such as double-tailed and elephant-eared bettas, often accidentally damage their elegant fins in their tank décor or are bitten by other fish in the aquarium.

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


Betta fish are prone to this disease because they have those long, graceful tails. Female bettas and shorter-finned varieties, such as the plakat, rarely develop fin or tail rot. It’s the price that luxury male bettas pay for having such striking and elaborate fins.

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

Stress is often the root or ultimate cause. It is normal for an aquarium to have colonies of bacteria and even fungi present in the water. A healthy fish does not usually have problems living with these organisms. But when your fish is stressed, its immune system breaks down and allows the infection to run wild.


How can you tell if your betta fish is getting sick? The first signs are usually very nonspecific and mild. Your betta fish may be under stress or become ill if:

  • Their appetite decreases or they refuse to eat.
  • Its general color is unusually dull and pale.
  • Betta fish fins look wavy or are curling along the edges.
  • They are pecking at their own fins or rubbing their fins and/or body along the substrate or aquarium decoration.

If you notice any of these signs of stress, you should check out your tank and see if you can identify any issues with your setup. If your betta fish is developing fin rot, you may be able to stop 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 necessary. Once things progress to moderate or severe, it’s usually obvious that fin rot is what you’re dealing with.

Fin rot stage Symptoms Diagnostic Notes
Mild – Backward or irregular edges to the pectoral, dorsal, anal and/or caudal fins.
– New red or brown look on the edges of the fins.
– White spots or whitish appearance along the edges of the fins.
– Early stages may resemble fin loss, but are usually spread over a wider area.
– If signs appear on more than one fin or along the entire edge of a fin, the fin is likely to be rotten.
– If whitish spots/growths start to appear on the body or head, it is probably not due to fin rot, but another infection such as ich.
Moderate – Partial deterioration of the fin or multiple fins.
– Black or reddish (bloody) fins with noticeable loss of tissue along the edges, moving towards the body.
– Fuzzy-looking growth along jagged edges of fins (but not on head or body).
– If your betta fish has fins with red or black edges that look like they are melting towards the body, it is probably fin rot.
– If you have made changes to your aquarium setup, but your betta fish ‘s fins look worse, it is progressing and needs more aggressive treatment.
Serious – Fin deterioration progresses more than halfway down the body.
– The total loss of the fins or the tissue between the rays of the fins.
– The base of the fin next to the body is swollen, bloody or turning black.
– Loss of scales and open sores in the areas of the body closest to the infected fins.
– White growths or whitish film progressing from the fins to the body and/or head.
– Your fish may stop eating and have trouble swimming or staying upright in the tank.
– Their immune system also fails, which can lead to your betta succumbing to other illnesses or parasites unrelated to fin rot.
– Once the disease progresses to your body, it can be very difficult to cure.
– At this stage, your betta fish may not recover, so immediate treatment is required.


What should you do once you have diagnosed your betta fish with fin rot? The first thing to do is check your aquarium setup and see if you can identify the reason for the illness. There’s no point in treating your betta fish until you’ve fixed the underlying problem in your tank, and for mild cases, that might be all the cure you need!


Remember, the microorganisms behind fin and body rot are almost always present in your aquarium water. If your betta fish develops signs of fin rot, there is likely a reason its immune system suddenly shuts down, making it vulnerable to infection.

The most common reason a betta fish gets sick is stress, and the most common reason for a stressed betta fish is improper or poor water conditions. If you are having problems with the conditions in your betta tank, the reasons could be:

  • The water temperature is outside the ideal range of 75°F to 86°F.
  • The water temperature fluctuates more than a few degrees during a 24-hour period.
  • There is no heater in your betta fish tank.
  • Water changes are infrequent or not done on a proper schedule.
  • The tank is too small for your betta (less than the recommended 5 gallons).
  • The tank is overcrowded with plants and decorations.
  • There are too many other fish or aquatic species in the tank with your betta.


Once you’ve reviewed your setup, you’ll probably have a good idea about the possible cause(s) 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 fish may recover without further treatment.

Your fish should recover fairly quickly from a mild case of fin rot. If your betta fish does not show improvement within two weeks of making these changes to your tank, or if the disease progresses further, you will need to take more drastic measures to treat them. You might even need to use a hospital tank.


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

Why do aquarists use hospital tanks? The problem with treating a sick betta fish in a community tank is that the cure itself can be toxic and stressful. Many drugs kill living 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 fish makes frequent water changes easy. Even if you only have one betta, it may be better to deal with a hospital tank for treatment than your usual 10-gallon setup. You should always use a 1-stage filter on these tanks, as medications can reduce the amount of oxygen carried by the water.


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

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

You will first need to mix the salt and water solution in a bucket and add it to the hospital tank before acclimating your betta fish to the new setup. If you are dosing a community tank instead of using a hospital setup, make sure the other animals can handle the salt at that concentration.

To treat fin rot on your betta fish with aquarium salts:

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

During the 10-day saltwater treatment:

  • Change 50% of the water in the tank every day, adding the same amount of pre-mixed saltwater solution.
    • The water should be the same temperature as your aquarium when you add it to the hospital tank.
  • Make sure the salt concentration stays the same no matter how much water you change, or you could 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 would mix 1.5 teaspoons of salt into 2.5 gallons of water to create the same concentration for a 50% reduction. Water. change.
  • It’s best to mix only as much saltwater solution as you need for a single water change, rather than make a large batch and store it for later use.
    • As the water evaporates, it leaves behind the salt. In a few days, the concentration of salt in the solution will increase as the water level drops, potentially poisoning your betta fish.
  • Monitor your betta fish ‘s appetite and look for signs of improvement. While your betta fish is being treated, give your main tank a good cleaning and rinse of substrate, decorations and live plants before adding fresh tap water and restarting the tank.


If your betta fish does not improve while using aquarium salts, or if you did not notice the disease until it progressed to a severe level, you will need to take the next step in treatment. This means that you will have to use medication in your aquarium. If your betta fish has other infections from its weakened immune system, medications will cure those as well.

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

Follow package directions and end treatment even if your fish improves quickly. The time period will vary depending on the medicine you use. You may need to go through several rounds of treatment to cure your betta’s fin rot:

  • Keep your aquarium at 78°F to reduce bacteria activity.
  • Perform water changes as directed on the package and be sure to add the proper amount of medication after water changes to keep the medication dose consistent.
  • A sponge filter or 1-stage filter is a must when using meds in your tank, but make sure there is no media in the filter or it will remove meds from the water.
Fin rot stage Treatment Average time of improvement and healing?
Mild Modify the aquarium setup to suit the ideal conditions for betta fish.

It may include upgrading to a larger tank, adding a heater and/or filter, removing decoration and/or excess tank mates, and increasing the frequency of water changes.

– Raise the water temperature to 82 o F for three days.
Use an over-the-counter white spot disease medication to treat the tank.
– If the improvement is not noticeable or if the betta declines further, treat moderate fin rot.
Moderate Same as mild, but also requires setting up a hospital tank and medicating with aquarium salts. – The improvement should be noticeable in a few days and noticeable after a week.
– You do not need to continue treatment once the fish improves and appears to be healing.
– You should not use aquarium salts for more than 10 days in a row.
– Full recovery time depends on the level of injury, but is usually no more than 2 weeks to a month after the infection is treated.
Serious Same as mild, but also requires the setup of a hospital tank and the use of antibiotics and/or antifungal medication to treat the fin rot and any secondary infections your betta may have developed. – If an improvement is to be seen, it should be noticed within the first 24 to 48 hours of treatment.
– A typical course of treatment is 3 to 5 days, depending on the medications used.
– Full recovery depends on the extent of the injury and damaged fins may never return to their original appearance.
– Severe cases may require several rounds of medication to clear the infection.


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


A: It depends on how long your betta fish has been sick and the severity of their illness, but you will quickly notice that your betta fish is getting better if you are using the proper treatment. Within a day or so they should look a bit brighter and be more active. If you have stopped eating, you should notice that your appetite improves as well.

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


A: Bettas with mild to moderate cases of fin rot usually make a full recovery, although it may take a few weeks for the tail or fins to grow back. Like human fingernails, betta fish fins typically grow a few millimeters a month.

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 fish lost a substantial portion of its fins, the damage may be too extensive and the scarring permanent.


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

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


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

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


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 of it. While you can’t completely eliminate bacteria or fungus from your tank, you can ensure that your fish stays healthy so that it’s unlikely to develop an infection.

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

  • Keep them in a spacious tank (5 gallons or larger).
  • Don’t fill them with too many decorations or tank mates.
  • Use a heater to maintain your ideal temperature range (75°F to 86°F).
  • Follow a regular schedule for filter maintenance and water changes.
  • Do not overfeed or underfeed your betta fish.


Fin disease is a common problem in betta fish with long, sleek tails, but it is very treatable if you catch the infection early. Once the infection progresses to body rot, a betta fish’s chances of survival are low. Simply making a few small changes to your aquarium setup can drastically reduce your betta fish’s chance of infection.

Low or inconsistent aquarium temperatures and infrequent water changes are the main cause of this disease. Most betta owners will experience rot at some point, so you need to know the symptoms and how to cure them. The quicker you fix the problem and treat your fish, the better chance your betta fish will make a full recovery.

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