Guppy Fin Rot: How To Treat It & Why It Happens

Last Updated on 2023-12-22

Guppy fin rot can be treated easily if it’s spotted early enough. However, if you leave it too long, or you don’t realise your guppy has it, then it can become fatal. In this article you’re not only going to find out what fin rot in guppies looks like, but you’ll also learn the causes, how to treat it and how to prevent it as well!

So keep reading to find out everything you need to know to keep your guppies alive!

Key Takeaways:

  • Guppy fin rot is a common issue that can be fatal if not treated promptly. It is caused by bacterial or fungal infections and can result from poor water conditions, stress, or injury.
  • Symptoms of guppy fin rot include red or sore fin tips, color changes in the fins, tattered edges, and, in severe cases, rotting fins and body.
  • Treatment for guppy fin rot varies based on its severity, with options such as water changes, API Stress Coat, aquarium salt, and strong medications like API Pimafix or API Furan 2.
  • Prevention measures include regular cleaning, water changes, avoiding overstocking, using a filter, providing high-quality food, and quarantining new fish.

First Of All What Is Fin Rot And What Causes It?

Fin rot in guppies is caused by a bacterial or fungal disease, which slowly begins to eat away at your guppies fins and tail. Poor water conditions, stress or injury lead to fin rot and when left untreated for long enough it can be fatal.

Fin rot is also not just specific to guppies, but any fish with long flowing fins like bettas and goldfish.

What Are The Symptoms Of Guppy Fin Rot?

Fortunately, fin rot in guppies is pretty easy to spot, especially if you’re checking for symptoms regularly. However, it’s important to be able to spot all the different symptoms so you can figure out how serious the fin rot is, as well as whether it’s bacterial or fungal.

Difference Between Bacterial Fin Rot And Fungal Fin Rot

The first thing you’ll need to figure out is whether your betta is suffering from bacterial fin rot or fungal fin rot. Depending on how serious they are, they may need different treatments.

Bacterial fin rot looks uneven and often times the fins are going to look more ragged, than when it’s caused by a fungal infection.

Fungal fin rot on the other hand will appear more even across the fins. And this can also be accompanied by a white edge going across your guppies fins. (If you notice white spots, however, then it may be ich.)

What Are Symptoms Of Mild, Major, And Severe Fin Rot?

As well as trying to figure out whether it’s a fungal or bacterial infection, you’ll also need to know whether your guppy is suffering from mild, major or severe fin rot. Knowing how extensive the fin rot is will allow you to give your guppies the best treatment possible.

Mild Fin Rot

If your guppy has mild fin rot, then you may notice the following symptoms:

  • The tips of your guppies fins will look red and sore.
  • There may also be signs of irritation.
  • At an early stage, you may begin to notice the tips starting to change color. They may be brown, grey or white, or simply darker in color.
  • The edges may also be appearing tattered. However, it shouldn’t be that extensive at an early stage.
  • And, if the rot is only minor, it will only be at the edge of their fins.

Major Fin Rot

If you think that your guppy is suffering from major fin rot, then you don’t have time to waste. Major fin rot can often be fatal if left untreated. It weakens your guppies immune system massively, opening them up to a whole range of illnesses and diseases.

  • When your guppy is suffering from major fin rot, large amounts of their fin may have rotted away.
  • You’ll also notice that a lot of the fin that’s left will now be discolored. Often times it will be incredibly dark.
  • It will also be much more obvious that the fins are starting to die completely.
  • If it’s a fungal infection there may also be a white fuzz on the fins.
  • Lastly, if you’re watching the tank, you may even notice whole clumps of fin falling off at a time.

Severe Fin Rot (Body Rot)

Severe fin rot also know as body rot, is the extreme end of fin rot. This isn’t something that will happen overnight however, it can often take a couple of weeks before it gets that bad.

It’s important to note, that saving your guppy at this stage of fin rot is going to be extremely difficult.

  • At this point you may notice that the fins have been eaten away entirely.
  • In fact, not only have the fins been eaten away, but perhaps the body has started to rot as well.
  • And if it’s fungal, you may notice that a white fuzz is where the base of the fins used to be.

As well as this, in all cases, you may notice that your guppies don’t appear as active as normal. They may be a bit more lethargic and also lose their appetite.

fin rot, guppy

How Do You Treat Guppy Fin Rot?

The way you treat guppy fin rot will be dependent on how severe is it.

If fin rot in your guppy is still mild, you can perform water changes and monitor the situation. As the fin rot becomes more severe, you’ll need to move your guppy to a quarantine tank and treat them with aquarium salt.

Obviously, as the severity increases, the treatment will also become more extreme. However, if you take good care of your guppy and you look after them, then they should hopefully make a full recovery.

Just remember, that when something like this happens you should always speak to a professional who will give you the best advice.

Also, to treat fin rot, it’s always best to set up a quarantine take, and move your sick guppy to it. Not only, does this mean that any treatment won’t affect your other fish, but it also means that fin rot won’t be passed on.

And if the fin rot has been caused by bullying, then it’s also going to stop your guppy getting their fins nipped.

Severity LevelSymptomsRecommended Treatment
MildRed and sore fin tips, minor color changeWater changes, API Stress Coat
MajorLarge portions of fin rotted, dark discolorationQuarantine, 100% water change, aquarium salt
SevereFins eaten away, body rottingStrong medication like API Pimafix or API Furan 2

How To Treat Mild Fin Rot In Guppies

If your guppy is only suffering from mild fin rot, then you won’t need to do too much. Here are the steps you’ll need to take.

  1. The first step, is to siphon the gravel at the bottom of the tank to remove any waste or debris. Waste and debris can will feed the bacteria that’s causing fin rot.
  2. Once you’ve done this perform a 25% water change, to replace old water with fresh clean water.
  3. You should also be checking the water parameters to make sure they’re all acceptable. The parameters to check include pH, temperature, chlorine, ammonia, nitrite and nitrate levels. (If you don’t have a test kit, then I highly recommend the API Master Test Kit.)
  4. Once you’ve done all this, you should begin treating your guppy. API Stress Coat will normally do the trick for minor fin rot, however, always ask a professional what’s best for your guppy.
  5. Follow the instructions on the stress coat, until the fin rot clears up.
  6. You’ll also need to make sure you remove the carbon filter in your tank while you’re treating your guppy as it can destroy the medication.
  7. Keep monitoring your guppy to see how they’re getting on. You should notice some improvement after a few weeks.

Check out this video by Guppy Channel on how to treat fin rot in Guppies:

How To Treat Major Fin Rot In Guppies

If your guppies condition has moved passed mild fin rot and has instead moved to major fin rot, then the way you treat them will be different. Remember, while minor fin rot has some time to treated, major fin rot will be needed to be treated as soon as possible.

  1. When you notice that one of your guppies has fin rot, you’ll need to immediately move them to a quarantine tank. Use water from your old tank to help acclimatize them.
  2. In your main tank, perform a 100% water change and clean as much of the surfaces as you can. This should help stop other fish from catching fin rot.
  3. Now mix aquarium salt with water and let it dissolve. Once it’s dissolved add it to your quarantine tank. (The amount you’ll need to do use will be on the box).
  4. When you’re using aquarium salt you’ll need to do a 100% water change every day. And when you’re using aquarium salt, make sure you’re not putting it into the same water twice.
  5. Keep doing this for the recommended amount of time (which will be on the box). Don’t use aquarium salt again until it’s safe to do so. Which is normally about a week.

How To Treat Severe Fin Rot

Lastly, this is how you can treat severe fin rot. However, remember, when your guppies are suffering from severe fin rot, there’s a strong chance they’re not going to survive. You’ll also need to use much stronger medication such as API Pimafix (if it’s fungal) or API Furan 2 (if it’s bacterial).

  1. The first thing you’ll need to do once again is to move your guppy to a quarantine tank. However, this time the quarantine tank will also need an air bubbler. Some medications can remove the oxygen out of the water, so an air bubbler will make sure enough oxygen remains.
  2. Once your guppy is in the quarantine tank begin dosing the tank with the recommended amount of medication. You’ll have to figure out whether your guppy is suffering from bacterial or fungal fin rot first.
  3. Make sure you’re performing 100% water changes before dosing your guppy again, otherwise you could poison them.
  4. While you’re doing this, you should also change 100% of the water in your other tank, as well as cleaning it, to make sure you’re reducing the chance of other fish from suffering.
  5. Once the treatment is over and you notice massive improvements, you can move your guppy back to the original tank.
fin rot, guppy

How Do You Prevent Fin Rot In Guppies?

Fortunately, fin rot is fairly easy to prevent. And it’s always better to prevent something from happening, rather than having to treat it. Here are a few of the ways you can stop guppy fin rot.

Preventive ActionWhy It Helps
Regular CleaningReduces bacteria and stress
Water ChangesMaintains water quality
Avoid OverstockingReduces stress and aggression
Use a FilterKeeps water clean
High-Quality FoodBoosts immune system

Clean Your Tank Regularly

The best thing you can do is clean your tank regularly. The amount you’ll need to clean your tank will depend on the size of the tank and how many fish you have. The less you have the less you’ll have to clean it, however, the more overcrowded your tank becomes, the more you’ll need to clean it.

Perform Water Changes

You should also make sure that you’re performing frequent water changes as well. Once again, the size and stocking of the tank are going to determine how often you’ll need to change the water.

Smaller tanks may need the water changing every 3-4 days, whereas bigger tanks can go a couple of weeks without having the water changed. Depending on how many fish you have.

Don’t Overstock Your Tank

Overstocking your tank is going to increase the chance of fin rot for three reasons. First of all, the increased bioload from all the fish will increase the chance of bad bacteria growing in the tank.

Second of all, overstocking your tank is going to stress out all of the fish. Not only will the tank become much dirtier much quicker, but they also won’t have enough space for their own territory. Becoming stressed by this, will weaken their immune system.

And lastly, the more fish you have in your tank, the more likely it is that your fish may start acting aggressive to each other. If aggression increases, then fin nipping may occur. Which can often trigger fin rot in guppies.

Use A Filter

Filters are essential to keeping your fish tank clean. It’ll constantly cycle the water removing a lot of the debris, waste, and ammonia in the tank, which can stress your guppies out and make them sick.

(Find out more about why guppies need filters.)

Use A Heater

Guppies are tropical fish, so it’s also important you make sure you’re using a heater to keep them warm at all times. Even if you think the water in your home is warm enough, sudden fluctuations such as from a draft can cause temperature shock which can stress your guppies massively!

(Find out more about why your guppy needs a heater.)

Remove Any Bullies

If you have bullies in your tank, then you may need to move them to another one. The more bullying that occurs, the more likely it is that a fish will get sick.

If you don’t have another tank to put the bully, then you can always try to take them back to the shop.

However, if this doesn’t work, then you can also try adding lots of hiding places in your tank.

(Here’s an article about all the great fish you can keep with guppies!)

Give Them High Quality Food

You should also make sure that you’re feeding your guppies the best food possible. Low-quality food isn’t going to give them the nutrition they need which will compromise their immune system.

High-quality food should cater to their dietary needs, which needs both plant matter and meat. As well as this, you should also feed them live food every once in a while as well.

To find out more about the best food for guppies check out this article. (Or here’s an article if you just want to find out more about what guppies should eat.)

Quarantine New Fish

When you’re keeping guppies and you plan on adding new fish to the tank, it’s vital you quarantine the new fish for two weeks beforehand. Doing this will allow you to see if they’re sick, and treat them before they spread the sickness to the rest of the tank.

Reduce Their Stress

You can do plenty of things to reduce your guppies stress as well. First of all try adding a lot more hiding places to your tank so they can have places where they feel safe. As well as this, you should also making sure you’re keeping enough guppies together, that the water is clean and healthy, and that they’re being fed regularly.

(If this all seems like a lot check out this helpful article on how to setup a guppies tank!)

Guppy Fin Rot_ How To Treat It & Why It Happens

Is Fin Rot Contagious To Other Fish?

Fin rot is an extremely contagious illness. If you don’t act quickly to stop it, it could spread to most of the other fish in your tank as well.

So if one of your fish is suffering from fin rot, make sure you perform a 100% water change in your main tank as well as cleaning the tank as best you can.

Once you’ve done this monitor your fish closely to make sure no more suffer from fin rot.


Now you know what causes guppy fin rot, how to prevent it, the symptoms and most importantly how to treat it!

Remember, the best thing you can do is make sure you’re keeping your tank clean and that you’re not overstocking it. If you do this you’re going to drastically reduce the chance of fin rot occurring in your tank.


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