Do Fish Heal Quickly? How do Fish Heal Underwater?

Pretty sure this is something that might not have crossed your mind. I too was boggled with this question when my six-year-old came running to me one day and asked, “How do fish heal under all that water? Doesn’t their blood get mixed up?”

Completely at a loss, I began my search to find out how quickly a fish healed and how they were able to overcome their injuries underwater.

This is what I found out.

It is impossible to tell whether fish heal quickly or not. Compare to other animals, the healing time is pretty much the same. When it comes to healing underwater, fish do so in the same way that other animals do on land. A lesion appears, which leads to immuno-responses and that in turn regenerates the skin. Simple!

Of course, this is not something that you can quote to your child of six. They need a lot more information to be able to process how fish heal underwater.

Or it might be that you are looking for answers because your fish has injured itself and you want to help.

This is exactly the right place you have come to. Here we have all the answers, informative ones, and practical ones.

Do Fish Heal Quickly?

No research or study confirms the fact that aquatic animals, fish, in particular, heal faster than any other living being. This means that fish heal at the same rate as any other animal. So no, fish do not heal quickly.

There is some research by a Georgetown University Medical Center scientist, Michael Zasloff who published a letter in the Journal of Investigative Dermatology, that stated Dolphins have miraculous healing powers. According to his study, Dolphins have a way of diving in the water that curtails excessive blood flow from a wound.

What’s more, unlike other animals, dolphins are less reactive towards their injuries and are able to perform normal tasks without feeling too much pain. The researcher also noticed that dolphins also seemed to have a remarkable ability to heal completely without any kind of distortion after injuries the size of two footballs! And all that within a few short weeks!

There simply is not enough research on the topic to conclude whether it is just dolphins or other aquatic animals as well that can make such remarkable recoveries in so little time.

So the answer to the question of whether fish heal quickly can be a clear no at this point in time.

How To Save Injured Fish? (Vide0)

Now comes the second question, how do fish heal underwater?

How do Fish heal Underwater?

As mentioned above, they do so the same way as every other animal. Here is what you need to know.

Fish heal much as we do: a lesion occurs, immuno-responses occur, the skin regenerates. This means that their process of healing is the same as other animals, including humans.

What is this process? There is how the animals’ system repairs their injured sites:

  • Once an injury occurs, the blood on that site starts to clot almost immediately. Within a few minutes, the bleeding stops completely.
  • This clot then forms a kind of scab which ensures that no germs can try to get inside the wound site and cause an infection.
  • The site of the wound then becomes swollen, red and tender. This is because the skin has not regenerated yet and the wound underneath the scab is fresh.
  • At times there is oozing clear liquid coming out of the wound. This is body’s way of cleaning the injured place.
  • Blood vessels are open near the open would as oxygen, as well as nutrients,  are required for healing of the injury.
  • It is the responsibility of the white blood cells to fight for any kind of germ invasion, along with the repair of the injury.
  • Over the following days, the system of the injured animal starts to repair all broken or damaged blood vessels, as well as creating new tissues.
  • Collagen is produced with the help of red blood cells. It is basically tough, fibrous white mass that aids in the formation of new tissues.
  • At this point, new tissues start covering the site of injury and the wound has new skin over it.
  • The more the wound heals, the smaller it gets as new skin is taking over the opening.
  • First, there appear scabs, which then fall off to reveal the new, slightly red and shiny skin.
  • A scar forms over the wound as it takes some time before the injured place the same as it used to before being injured.

This is the basics of injury healing that is similar for all animals, including fish. There are of course certain differences that make fish unique in their healing abilities.

What set’s them apart is that they very rarely catch any kind of infection which would further aggravate their wounds or delay full recovery. The reason fish don’t often develop an infection is that they have three things protecting them; touch skin, scales and a slimy coating that helps in slipping the bacteria and parasite off.

The slime coat is what makes a fish so slimy when touched. This substance is produced all the time and a fish never runs out of it. For people who have fish in a tank or aquarium, keeping a fish that has gotten some kind of parasite, in a salt bath would help in replenishing the slime coat of the fish. This would then aid in getting the parasite off.

The second thing protecting the fish is its scales. They are 3 times more difficult to cut through than human skin, which is why it is very difficult for an infection to pass through, even if it manages to get through the slime coat. They are a kind of armor for the fish.

Then comes the skin of the fish, which is no less tough than the scales. Therefore, even though the injury is on the skin, the infection finds it next to impossible to manage its passage through the slime coat and then the scales.

And this is the reason why, unlike humans and other animals, fish heal without getting infected with any other kind of parasite when they get injured. Hence, an easy recovery.

One more thing you need to understand is that heavy bleeding only occurs when a major organ like the kidneys or heart is pierced. There is only superficial bleeding from other cuts.

The fish also does not have any major blood arteries or veins in its musculature, which is what lies above its major organs. Thus, no excessive bleeding since nothing major is damaged in small injuries.

What’s more, fish do not have scars like humans. Their skin completely regenerates so that it is the same as it used to be before it got injured. This is the reason why scientists are so interested in learning more about the healing abilities of fish scales and skin.

Healing An Injured Fish at Home Underwater

If you have an injured fish at home, then the first thing to do is not to panic. In most cases, just a simple remedy can work wonders for your little guppy.

The very first thing you need to do is to isolate your fish in another tank of clean water. This way, no more fish or their environment will be affected because of the germs from your injured fish’s wounds.

What’s more, if your fish was injured in a fight, there would be no more chances of any further violence inflicted on the poor thing. The fish would get enough time to heal in a secluded place where it is safe from anymore fights with other fish of its tank.

Here are some steps on how you can help in the healing of different body parts of your pet fish.

How to heal fish fins

Most of the time when fish get hurt, it is because they have been unable to get along with their tankmates. Aggressive fish end up nipping the fins of the more docile fish. If you have a betta, chances are their long, brightly colored fin are at the danger of getting injured in a fight.

Of course, if the opposing fish is particularly hostile, it can also bite and damage the scales of its competitor.

In most cases, the injury is not bad enough to warrant a visit to the vet. All you need to do is put in some conditioner additive that helps in maintaining the healthy slime coat on your docile fish’s body.

It is the slime coating that helps in protecting the fish’s body from different kinds of infections and germs. Once the fish has healed, you may want to keep them separate from the offending fish.

Presence of Collagen

As per research, collagen is present in a fish. This is believed to be the one thing that aids in regeneration of cells. According to science, bony fish have the ability to literally grow back any kind of cell they wish to, so long as it is not any major organ damaged beyond repair.

This perhaps is another thing that promotes complete healing in fish when they get injured. Even though scientists are sure about the function of collagen, there is still need for more research to discover how far the healing capabilities of fish go.

Healing Eye Injuries

Since fish have protruding eyes, they are very susceptible to injuries, particularly in fights. Fish like black moors, who have telescopic eyes extending from their head are most prone to eye injuries. Other fish that experience eye injuries frequently include bubble-eye goldfish, telescope goldfish, and celestial goldfish because they too are bulbous-eyed fish.

You will notice the damage when you see a cloudy spot on the cornea of your fish’s eye. The best course of action is to separate your fish to a new tank and let them recover in peace. Pour in some water-conditioning agent as that will promote the fish’s healing slime layer to form on the eye and speed up the process of recovery.

The Use of Shrimp for Fish Injuries

One scientist at the James Cook University of Australia had discovered in 2018 that shrimps were able to not only remove the parasite from a fish, they were also able to heal the wound they had gotten.

He found out that the injuries on a fish were relatively less red once they had been cleaned up by shrimps. What the small shrimp does is pull out the bacteria and dead tissue from the site of injury and then reduce stress levels of the fish. This promoted healing of the wound quickly.

So what you can do is introduce shrimps in the tank where you keep an injured fish. This way, their healing process would speed up and become even more effective.

Fish Fin Rot

Fish fin rot is a disease, unlike damage to the fish scale or tattered fins. It causes the fins of your fish to become fizzy and jagged on the outskirts, which eventually with time, start to disintegrate.

The most common cause of fish fin rot are gram-negative bacteria like the Pseudomonas, Vibrio or the Aeromonas. Keep in mind though that this bacteria is put into already open wounds by an opponent fish.

Fish fin rot mostly takes place in environments where there are too many fish in the same tank and the nitrate levels have risen beyond safe.

 In order to fully and successfully treat a fish with fish fin rot, you will need to follow a series of steps. Start by putting the diseased fish in a separate tank. Then apply a natural antibacterial product on their fins.

You can also give them strong antibiotics like tetracycline or oxytetracycline. But it is best to consult with a vet before giving any kind of antibiotics as they can put your fish in stress.

Once the disease has been cleared or while the treatment is ongoing, make sure to clean up the aquarium properly. You will also need to maintain the right temperature and pH of the tank to avoid any kind of bacterial growth in the tank. Be sure to not overfeed the previously diseased fish.

Visit a Vet

It is true that most eye injuries heal on their own, with a little special care from you, since the majority of the injuries are superficial and don’t really need any kind of medication.

There are other times though when the injury is too deep and needs to be dealt with through proper medication. This is the time when you will need to take your fish to a veterinarian. They will be able to suggest some specific care, along with recommendations on what medicine to give.

You will also need to consider the idea of euthanasia when the injury is beyond help. This happens when the fish has gotten so badly injured that they even stop eating. The vet will suggest how you can take your pet fish out of their misery.

Frequently Asked Questions

Does a fish’s mouth heal after it has been hooked?

Yes, it does, but it takes time to heal completely. Bony fish, those are almost all the fish with backbones, are ones who can heal completely from any kind of injury. This is because bony fish have the regenerative ability to recover themselves completely from almost any kind of injury. Hence the reason why a fish would have a completely recovered mouth after some time, even if it was once hooked.

Can fish grow their eye back?

Fish have regenerative abilities and are able to treat injuries to the retina at the cellular level. This means that if the injury is not too deep, then yes the fish can literally grow its eye back. The extent of the injury is what determines whether the cells can be regrown, but in most cases, so long as it is a bony fish, the wounded eye will be good as new.

Do fish die after they are caught on the hook and then released?

This depends on what kind of injury they have sustained. If the hook only injured their mouth, then there is no cause for the fish to die. Since fish have regenerative abilities, they are able to grow back all the cells of their wounded mouth and become as good as new. Of course, this takes time, but it happens.

If on the other hand, the fish gets its swim bladder ruptured, then the chances of fish recovering from this injury are very limited. This rupturing bladder occurs not because of the hook, but because of the sudden pressure a fish experiences when it is removed from the water and brought into the open air. If the bladder is damaged there is no way the fish can survive.


So now you know that fish do not heal quickly, as there isn’t enough evidence to support the claim. And you also know how fish heal the same way underwater as any other animal does on land. You also know how you can help your fish who have acquired an injury in recovering successfully.

It is true that bony fish have been blessed with a remarkable ability to heal completely from most types of injuries over time, but this does not happen quickly. This means that even if they lose a fin, they can grow it back in time. This regenerative property is found in bony fish and not cartilaginous fish.

Remember, there are theories that fish skin has faster and more effective healing properties, but the research is still too new to be sure about. Whether or not saltwater or freshwater aids in the recovery of fish injuries is yet to be discovered.

If you feel there is something wrong with your fish, they are injured or ill, and you don’t know what to do, don’t wait around, take them to a vet immediately.

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