Fin Rot Treatment, Causes & Symptoms

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A helpful post covering fin rot treatment, causes, and symptoms to help you identify the disease and most importantly, how to treat it effectively.

Fin Rot Treatment, Causes & Symptoms

When it comes to your fish, there is a very severe disease that can quickly kill them, and it is called fin rot. This is a disease that pretty much any fish you have in an aquarium can develop, one that is deadly if left untreated. Fish are family, and we obviously don’t want to see any harm come to them, so we are here today to find out all about fin rot treatment, the causes, and symptoms.

What Is Fin Rot & How Is it Caused

Fin rot is not actually a disease that fish catch develop by themselves, but it still is a very harmful thing for any fish to suffer from. (We personally recommend this treatment). Fin rot is a very deadly disease that will quite rapidly cause your fish’s health to deteriorate physically, and if left untreated, it can definitely become fatal. Fin rot is a disease that is most often a secondary condition caused by other harmful bacteria in the water.

Fin rot will start to happen in a fish once it has suffered some kind of wound where the flesh is exposed. This is then coupled with an increased presence of certain bacteria in the water, which then ends up causing this deadly condition. The bacteria most common for causing fin rot include ones called pseudomonas, aeromonas, and flexibacter.

This may sound somewhat alarming, and even more alarming is that all of those bacteria are inherently present in your aquarium, but they can only cause fin rot when the conditions are right, or in the case of your fish when the conditions are wrong.

These bacteria become very dangerous and can cause fin rot when the tank is unclean, which means that it is full of waste, nitrites, nitrates, and ammonia (more on lowering Ammonia levels here). These bacteria can also cause fin rot to occur when the tank is overstocked with fish and/or plants, if the fish is injured, or if the fish is stressed out.

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Types Of Fin Rot: Mild, Major And Extreme

There are three types of fin rot which we have to talk about. Now, to be clear, these are not so much different types of fin rot as they are different stages in the progression of fin rot. Let’s quickly go over what each of these three stages entails and what to look out for.

Mild Fin Rot

This kind or stage of fin rot consists of the mild tattering of the fins, slightly darker color or changing the color of the fin tips, it is usually only present near the tips of the fins, and there will be small amounts of redness or irritation along the fins, especially near the tips. It is one of the early stages to watch for.

Major Fin Rot

This stage of fin rot is much more serious. It consists of very severe damage, tattering, and tearing of the fins, and some chunks of the fin may even be missing.

The tips of the fins, as well as a good portion of the rest of the fins, will be dark and discolored, more than just the tips of the fins are affected, the fins severely recede towards the body of the fish, and the fish will look kind of red, bloody, and be covered in this weird fuzzy substance.

Extreme Fin Rot

TThis stage of fin rot does not really qualify as pure fin rot anymore. At this point in the stage of the disease, the fins will be more or less black or severely discolored, will be completely tattered and rotted off, the fish will be very fuzzy, red, and have irritated skin.

For all intents and purposes, at this stage, the fin rot has turned into full body rot. If extreme fin rot is not treated immediately, it will quickly spell the death of your fish.

What Are The Main Symptoms Of Fin Rot

There are several obvious symptoms of fin rot that you will see on your fish if they are suffering from this disease. Here are some of the most common symptoms that you should be able to identify in order to tell whether or not your fish is suffering from fin rot.

  • At first, if your fish has fin rot, you should notice milky white patches developing around the edges of your fish’s fins and tail.

  • As the disease progresses, it will cause a ragged or tattered look on the fins and tail of your fish, kind of like the frills on a carpet.

  • The fins of the fish, as well as the tail, will begin to darken, become discolored, and literally look like they are rotting away.

  • As the disease progresses even further it will eventually eat away at the skin or membrane of the fins and tail, leaving only the fin rays exposed as all of the fin membrane is rotted away.

  • If fin rot is left to progress even further, it may also work its way up the tail and fins and start to affect the body, in which case many people refer to it as body rot.

  • There are also secondary infections that may occur afterward. Many people note that their fish seem to be covered in some kind of white fuzzy substance.

Fin Rot Treatment, Which is The Best?

There are several different fin rot treatments but we personally feel these 3 are some of the best fin rot treatment options.

1. API Melafix Antibacterial Fish Remedy

This is a great fin rot treatment to go with, probably one of the best one out there in our opinion. This stuff will treat a variety of fungal and bacterial infections, so it works for fin rot as well as a few other diseases too.

This fin rot treatment simply needs to be added to the fish tank according to the directions on the bottle. This stuff is great because it will not kill good bacteria in the water, will not make it cloudy, will not change the pH, and it will not affect the biological filter either.

API Melafix is a great treatment for fin rot, tail rot, eye cloud, and mouth fungus. It also helps to heal wounds and abrasions, and helps to spur on the regrowth of new fin ray cells and fin tissue. We really like this particular treatment because it can be used for both fresh water and salt water aquariums.

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2. API Fungus Cure Powder

This is a great treatment option for taking care of contagious fungal infections as well as secondary bacterial infections. API Fungus Cure Powder works to treat fungus, mouth fungus infections, body slime issues, eye cloud, tail rot, fin rot, and in some cases it will even help treat body rot.

This stuff is great because it even helps prevent the growth of fungus on new fish eggs. All you need to do is to pour the packet of powder into the water and watch as your fish start to heal. API Fungus Cure Powder is only for use in fresh water aquariums and on a side note, it will cause slight cloudiness in the water.

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3. Kanaplex

Kanaplex is great solution for a large variety of bacterial and fungal infections such as dropsy, pop eye, fin rot, tail rot, body rot, and septicemia.

This is a useful choice to go with because it is absorbed by the fish and therefore also helps to cure diseases which leave the fish not wanting to eat any food. This stuff is pretty great because it can be used in both saltwater and freshwater tanks.

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How To Prevent Fin Rot

Fin rot is best treated by using preemptive strikes to your advantage, or in other words, this is a condition that is much easier to prevent than it is to treat. Here are some of the best ways in which you can prevent this deadly disease from affecting your fish.

Fish Compatibility

Fin rot is a secondary infection caused by bacteria, and it often takes place when a fish has a wound. Therefore, you want to make sure to only house fish together that don’t try to eat each other and don’t nip at each other’s fins. Open wounds caused by other fish are highly susceptible to developing fin rot.

No Overcrowding

Fin rot is also something that happens in overcrowded tanks, so making sure that your tank is not filled up to the limit with fish is another good way to prevent it from occurring. Most fish experts would agree that you should have no more than one square inch of fish per every gallon of water in the tank.

The more fish there are, the less space they have, the more waste and bacteria they swim around in, and the more likely they are to become aggressive and nip at each other.

Cleaning The Water

Perhaps the best way to make sure that your fish do not develop fin rot is to ensure good water quality. You absolutely need to change at least one-third of the tank water every week, or even twice per week if you have a lot of fish.

If you want to keep bacteria at bay, you also need to make sure to have a filter that does a fantastic job at filtering a variety of waste, bacteria, and other pollutants out of the aquarium water.

Fin Rot FAQ

Should I really be concerned about fin rot?

It is one of the most common diseases plaguing aquarium fish and is also one of the most easily preventable diseases as well. So, yes. If you are an aquarium fish owner, then fin rot infection is definitely something you should be concerned about.

It is a highly treatable fungal infection that can be helped with medication and a change in the environmental conditions in their habitat. However, it can also prove to be challenging to treat if you let it go untreated for too long.

Can the fins grow back after fin rot?

If you treat the fin rot before it reaches the fins down the body, then the fin tissue can regrow. If not, the fin tissue will not grow back, and the disease may progress and enter the goldfish's body and ultimately kill it.

What are the behavioral signs of fin rot?

As the fins of your fish begin to deteriorate, the fish may become listless and will do what they can to seek any kind of relief. To do this, they may rub themselves against the tank as well as any decorations you have in the aquarium. Other than this, the disease shouldn't cause any other behavioral problems.

Can aquatic plants help prevent Fin Rot?

Java moss and Java ferns can be added to the aquarium because these live plants can help filter the water and keep the tank clean. However, it is also important to note that goldfish love to munch on many aquatic plants, so you always need to have some kind of filtration system in place as well.

Is fin rot contagious?

Fin rot is not contagious; however, any sick fish should still be kept in a separate tank and away from all the healthy fish. Healthy fish can easily become stressed when there are contaminated water conditions, and this can ultimately cause them to develop a weakened immune system.

What causes fin rot?

Fin rot is most often caused by different types of gram-negative bacteria. These harmful organisms will begin to eat away at the fin's membrane, and they can then become susceptible to other secondary fungal infections.

Is it easy to tell if your goldfish has fin rot?

The most obvious signs of this disease include discolored fins. The edges of the fins may also appear to have a fuzzy, white lining as well and the fins may also develop red streaks due to inflammation and bleeding as a result of the disease.


Fin rot can be a truly deadly disease for any fish, and even if it does not cause death, it can leave permanent injuries that your fish will never heal from. As long as you follow the precautions we have talked about you should have no problems preventing this horrible condition and it's also very important to know how to treat fin rot.

That being said, nobody can always ensure that something like fin rot will not occur. It just happens, and sometimes it is completely out of your control, in which case you need to know how to identify the signs of fin rot. Finally, the treatment options we have discussed are by far your best bet in terms of treating fin rot.