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13 Common Killifish Diseases and Illnesses

13 Common Killifish Diseases and Illnesses

This post is written to the author's best knowledge and is not intended to be used in place of veterinary advice. In addtion, this post may contain affiliate links. As an Amazon Associate I earn from qualifying purchases.

Taking care of killifish should generally be a great experience. You’re going to enjoy your time with them because they’re easy to care for.

Many people buy these fish specifically because they have a reputation for being easy to keep. So long as you take care of the basics, there’s a good chance that you won’t have too much to worry about.

Even so, it’s possible that your killifish will get sick under the right circumstances. Killifish are susceptible to certain diseases and illnesses.

Knowing about these diseases and illnesses will help you to know what to look out for. Continue reading to get all of the important details so you can protect your fish.

1 – Slime Disease

Slime disease is a type of parasitic disease that you should look out for. When fish have this disease, it causes them to produce far more mucus than usual.

It’s notable because it makes the fish more susceptible to other diseases. Generally, this is caused by fish becoming very stressed in the fish tank.

You might need to be more careful to keep the tank clean. When killifish are forced to live in poor water conditions, it can make them sick.

Fish with slime disease will have difficulty breathing, and they might also lose their appetites. It’s common for fish to rub against objects in the tank to try to find relief as well.

This condition can be treated with medications such as formalin and copper sulfate. Raising the water temperature to 86 degrees Fahrenheit can help and so can using aquarium salt (as instructed).

2 – Ich

Ich is another parasitic condition that is also referred to as white spot disease. You’ll notice white spots appearing on the body of your fish.

These white spots indicate that your fish is dealing with parasites. Fish that are dealing with this condition will be very uncomfortable and will rub against objects in the tank.

They will stop eating and become rather sluggish, too. It’ll make it hard to breathe when the white spots are located near the gills.

Fish are more susceptible to ich when the conditions in the tank are poor. A poor diet can also make fish more likely to get ich.

Thankfully, this is a condition that can be treated. There are medications that can help to get rid of the parasites, and raising the water temperature also helps.

3 – Fin and Tail Rot

Both fin rot and tail rot are serious problems. As you might expect based on the name, this type of disease involves parts of the fish rotting away.

This is a bacterial infection that can happen when fish get injured. In overcrowded fish tanks, the fish might bite each other, and this will lead to fin rot or tail rot depending on where the bites occurred.

Poor water quality is known to play a role, too. Luckily, this is a treatable condition if you act fast.

You want to fix issues with water quality in the tank as soon as possible. Treat the fish with medications such as Melafix to get them back to normal.

Fish might wind up being permanently disfigured when they get fin rot or tail rot. Sometimes the fish will even die, but you can save the fish if you act quickly and use the right medication.

4 – Mouth Fungus

Mouth fungus is a type of fungal infection that killifish might sometimes have to deal with. It’s caused by mouth wounds and exposure to bacteria.

Fish are more likely to get mouth fungus if they are in bad shape. Poor water conditions and a bad diet will make fish vulnerable to this condition.

You must use antibiotics to treat this problem. You’ll need to speak to a veterinarian to get the best antibiotic for the fish.

Aquarium salt can help to keep this issue from spreading in the tank, but you should use it only as instructed. Be sure to feed fish well so they can have an easier time recovering.

5 – Pop Eye

Pop eye is a very noticeable condition where the eyes of the fish will bulge from the sockets. This is a disease that can impact one eye or both eyes.

Sometimes the eyes will be very swollen when fish are dealing with pop eye. The eyes will also likely appear to be cloudy and white during this time.

It’s a condition that can be caused by many things such as bacterial infections, parasites, viral infections, and fungal infections. Even accumulations of water bubbles in the eyes of the fish can cause such issues.

Injuries are known to lead to pop eye as well, and this is why you want to limit fighting in the fish tank. When a fish has pop eye, it’s best to isolate it and use Epsom salt to treat it.

Change the water regularly and make sure that the water parameters are exactly where they need to be. A fish can recover from this, but it can also lose an eye or go blind if things go wrong.

6 – Velvet

Velvet is a disease that is sometimes referred to as rust or gold dust disease. Killifish are very susceptible to this disease, and it can kill the fish if you don’t treat it.

This disease is caused by organisms known as Oodinium limneticum and Oodinium pillularis attaching themselves to the fish. This causes the fish to become irritated, and they will have a tough time breathing.

Fish with velvet will stop eating, and they’ll try to rub against objects. Poor water quality, temperature fluctuations, and general stress make fish more likely to get velvet disease.

Adding aquarium salt to the water can help to treat velvet. Medications such as Atabrine and copper sulfate are often used as treatments.

Raising the water temperature can help, too. Be sure to begin treating the fish as soon as you notice problems.

7 – Columnaris

Columnaris is an infectious disease that’s caused by column-shaped bacteria. This is a disease that is known to spread fast in fish tanks.

Sick fish will show signs of having ulcers on their bodies. You might also see white patches appear on the gills.

The gills may change in color, and the fish will likely appear to be short of breath all the time. Often, columnaris is associated with poor conditions in the fish tank.

The tank might be dirty, and you might not be feeding the fish adequately. Overcrowded fish tanks are more likely to deal with columnaris outbreaks, too.

To treat the fish, you’ll need to use antibiotics to give the fish a medicated bath. Lowering the temperature in the tank can help as well since columnaris spreads easier in high temperatures.

8 – Dropsy

Dropsy causes fish to have huge inflamed stomachs. Sometimes this condition is called bloat.

Fish that are stressed are more likely to have these problems. Dropsy is directly caused by bacteria, but problems with the water temperature will play a role in the fish getting sick.

Antibiotics can help to clear things up over time. You’re also supposed to solve problems with the water quality to get the fish healthy again.

Anything that was causing the fish to be stressed should be addressed. Feed the fish high-quality food, and it should return to being healthy.

9 – Swim Bladder Disease

Swim bladder disease is a problem that can cause fish to lose control of an organ known as the swim bladder. A swim bladder is a gas-filled sac that helps fish to control buoyancy.

When the swim bladder isn’t functioning properly, the fish won’t be able to swim normally. It can cause fish to swim erratically, and you might even notice them swimming upside down.

You might see that the fish will have a swollen belly when dealing with swim bladder disease. Sometimes this is caused by constipation due to the fish eating too much.

In such cases, you can get things back to normal by not feeding the fish for four days. Swim bladder disease can also be caused by bacterial infections and parasites, though.

Depending on what’s wrong, you might need to clean the fish tank better, raise the water temperature, and add some salt to the aquarium. If the fish is having trouble eating, it might be necessary to hand-feed it for a time.

Eventually, the fish should get better. Just do your best to treat the fish and be sure to avoid overfeeding the fish in the future.

10 – Anchor Worms

Anchor worms are parasites that can cause a number of problems for your killifish. When these fish have anchor worms, you’ll be able to see the worms stuck in their bodies.

This will cause significant irritation, and the fish will have red skin that is rather swollen. You’ll notice the fish trying to rub against the tank walls and rocks to try to get the worms off.

Often, these worms come to a tank when you add new fish to the tank. This is why you should quarantine newcomers for several weeks before adding them to the main tank.

It’s even best to quarantine aquatic plants since the worms might be carried by certain plants. You can contact an exotic veterinarian to get the worms out of the fish.

You’re supposed to use UV light to kill the remaining worms in the water. It’s best to try to avoid allowing your fish to get anchor worms in the first place.

11 – Hole in the Head Disease

Hole in the head disease is caused by a parasite as well. You’ll notice small wounds on the heads of the fish.

Eventually, the wounds will become larger, and the fish will appear to have holes in their heads. These lesions may or may not be bloody.

Fish that have this disease will often produce white and stringy fecal matter. They will eventually stop eating normally as things progress.

The fish will lose a lot of weight since they’ll stop eating. Hole in the head disease usually happens when fish are highly stressed.

Medications such as metronidazole can be used to treat the condition. Large water changes and raising the water temperature will be important as well.

12 – Cloudy Eyes

Cloudy eyes can be very troubling for your fish to deal with. This condition causes the fish to have cloudy eyes, and sometimes the eyes will turn completely white.

In some cases, fish that have dealt with this have wound up going blind. There are a few things that are known to cause this condition.

Poor water quality contributes to fish developing cloudy eyes. Elevated ammonia and nitrate levels in the tank will harm your fish.

Water temperature fluctuations cause fish stress. It’ll make them more vulnerable to getting sick.

Treating this condition involves cleaning the tank thoroughly and solving problems with the pH balance. Ensure that the nitrate and ammonia levels are in the right range.

Do regular water changes and add a bit of aquarium salt to the water. It can help the fish to recover, but there is a chance that your fish won’t regain its sight.

13 – Furunculosis

Furunculosis is a very contagious disease that can cause sudden death. This makes it especially scary since you might not have time to do anything to help your fish.

It’s caused by the usual problems in the fish tank. Poor water quality, temperature fluctuations, and excessive stress need to be avoided.

When fish have this disease you’ll notice that they will seem very tired. They might try to jump in the water a lot, though.

Fish with furunculosis usually have a hard time breathing. To treat the fish, you can get medications from a vet.

Final Thoughts

Now you’ve learned about the various illnesses and diseases that can impact killifish. Knowing what to look out for should help you to be vigilant.

Do your best to take care of the basics, and your fish will be so much more protected. After reading the information above, it’s easy to see that problems with water quality are often to blame for fish getting sick.

If you can keep the water quality high and feed your fish well, it’ll go a long way toward protecting them. Be a proactive fish tank owner and pay attention to the tank so you can take note of any problems as soon as possible.