Fish Disease: Symptoms, Care and Treatment

If you own fish at home, you obviously don’t want them to get sick. When fish acquire an illness or an infection, it can be difficult for them to cure on their own. Not only that, but it’s a hassle for you to get them medical attention from a qualified veterinarian. Given the difficulties, the chances of your fish dying when they’re sick increase drastically.

Because of that, you should keep them healthy and happy everyday. But how do you know if your fish is sick or has an infection? And if they are sick, what are you supposed to do? Given the confusion and lack of awareness around these instances, here is a complete guide to the most common fish diseases as well as their symptoms, treatments, and even how to prevent your fish from acquiring a disease, infection, or other harmful illness.

Types of Fish Diseases


Bacterial fish diseases and infections require antibiotics in order for your fish to be relieved from them. You can tell if your fish has a bacterial infection if it has red streaks, spots, or it’s swelling.


Fungal infections and diseases usually involve white or gray puffy spots and marks on your fish’s body.


Infections and diseases that involve parasites are most commonly treated using copper or malachite green treatments.

Physical ailments

Your fish my also have a disease that results from the environment that they’re in. For instance, fish can most commonly attract physical ailments if they have in poor water conditions. You can tell this is the case if your fish are gasping, not eating, or they’re attempting to jump from the tank (1).

Bacterial Fish Diseases

Fish TB

Fish Tuberculosis is a fish disease that’s not too contagious, and it doesn’t have any dramatic effects on your fish. That being said, it can be difficult to tell whether your fish has TB or not.


Fish TB is commonly caused by mycobacteria residing in the water of your fish tank. Not only that, but mycobacteria typically reside in locations that have poor water quality, which entails water that has little oxygen, low pH levels, and a large amount of zinc.


  • Lethargic
  • Hollowed belly
  • Pale color
  • Skin ulcers
  • Frayed fins
  • Scale loss


There is technically no treatment or vaccine for Fish TB, and your fish will most likely need euthanized if they attract TB. After you remove the infected fish from the tank, you should disinfect the tank directly afterwards in order to prevent others from acquiring the disease as well (2).


Dropsy is classified as a disease in which your fish’s whole insides fill with buildup. This accumulation of buildup causes damage to your fish’s internal organs and can result in death if not treated immediately.


Dropsy is typically caused by bacterium known as Aeromonas, and it most commonly affects fish that are stressed from over-crowded tanks.


  • Bloated
  • Scales that stick out
  • Extruding eyes
  • Lethargic
  • Loss of appetite


Unless it’s caught early, Dropsy is untreatable. If you fish is showing early signs of the disease, then you should isolate the fish and feed it antibacterial food.

Cloudy Eye

Cloudy Eye is defined as a fish disease that causes your fish’s eyes to have a hazy and white finish over them. If not caught early, it can lead to your fish losing their vision completely.


Your fish most likely has Cloudy Eye because of parasites in their water. Not only that, but they can also attract Cloudy Eye if they’re under severe stress, of an older age, or they suffer from malnutrition.


  • Loss of vision
  • Distress
  • Gray haze over your fish’s eyes


If you fish has cloudy eyes, you’re recommended to isolate them, disinfect their tank, and feed them antibacterial food. In addition to that, you should also monitor the tank water’s pH because that can drastically affect how your fish manages the disease (2).

Bacterial Fin Rot

Fin Rot is classified as a bacterial disease that begins at the fins and eventually destroys more of your fish’s body. Fish TB can also lead to this disease if not caught early.


Your fish may develop Bacterial Fin Rot if they reside in poor living conditions. Additionally, they may also attract the disease if they have a simple wound or injury on their fins that goes untreated in poor water conditions.


  • Milky white areas on fish’s body
  • Exposed fin rays
  • Disintegrating fins reduced to stumps
  • Blood on the edges of the fish’s fins
  • Reddened fins
  • Cloudy eyes
  • Skin ulcers


To treat this bacterial disease, you should disinfect the water with antibiotics. You may also find it beneficial to feed your fish food that contains antibiotics. Make sure to keep your fish’s environment clean after they’re treated (1).

Red Pest

Red Pest is classified as a disease in which your fish has red streaks all around their body because of bacteria in their circulatory system. The presence of this bacteria damages your fish’s tissues, vessels, and other internal organs.


Several different factors can cause Red Pest, including other organisms infected with the disease as well as an Ammonia spike in the tank’s water. Not only that, but your fish may also develop Red Pest if they’re forced to live in poor tank conditions, especially tanks that have high amounts of nitrate in them.


  • Internal bleeding
  • Red streaks all over their body
  • Discoloration on the flanks
  • Bulging eyes
  • Bloated abdomens
  • Gasping at the tank water’s surface


There is technically no cure for Res Pest, but it can be managed if it’s caught early enough. For instance, you should disinfect their tank as quickly as possible, and add antibiotics to their food.

Parasitic Fish Diseases

Swim Bladder Disease

Probably one of the most common diseases, Swim Bladder Disease is an illness that affects our fish’s bladder because of a parasite or other physical damage.


Swim Bladder Disease is generally caused by the compression of your fish’s bladder, and it can also be caused by a bacterial infection from a parasite destroying the inner workings of their bladder. It can also be caused by physical damage from your fish acting in destructive ways or other fish causing physical damage to your fish.


  • Swollen belly
  • Curved spine
  • Floating upside down


To treat Swim Bladder Disease, you need more than one single medication. Instead, you’ll need multiple different medications. Additionally, you should also expose your fish to warmer water and refrain from feeding them for up to three days. Try feeding them peas on the fourth day, and lower the water line of the tank (3).


Flukes are one of the most common fish diseases because it’s the name of a number of parasites. These parasites can attach to your fish’s body and then eat their flesh little by little. They can be extremely problematic if they attach to your fish’s gills, since this will affect the level of oxygen that your fish are able to retrieve.


Flukes are caused by bad environmental conditions, which include poor water quality, waters with high levels of ammonia, and overcrowding.


  • Layer of mucus on your fish’s body or fins
  • Gills look like they have been chewed
  • Reddened skin
  • Fish is scratching against objects


To treat your fish’s Flukes, you’ll need an anti-worm medication that you give to your fish several times a day. You should also disinfect the tank and isolate the infected fish (2).

Anchor Worm

Anchor Worm is defined as a parasite that damages your fish’s internal body structure and weakens it, opening an opportunity for your fish to attract more diseases.


Your fish can develop Anchor Worm if they’re exposed to a tank or a plant that has already been infected with the worms.


  • Redness around an anchor point
  • Skin ulcers
  • Inflammation
  • Red worms found at the base of fins


To treat Anchor Worm, you should give your fish medication, such as Potassium permanganate. Not only that, but you may also give your fish anti-parasite medication.


Argulus is also named as Fish Lice, and it involves your fish having lice attached to its body using their hooks and suckers. These lice stress your fish and can result in death if not treated accordingly.


Your fish may develop Argulus if they’ve been exposed to other fish that already have the disease. Lice have the ability to travel from fish to fish in the water, so the disease spreads quickly.


  • Small, dark spots on your fish’s body
  • Red markings
  • Skin ulcers
  • Inflammation
  • Restlessness


To remove lice from your fish, you should hold your fish with a damp cloth and remove the parasites with tweezers. After removing all of the lice, you should clean your fish’s wounds with antiseptic wash (4).

Fungal Fish Infections

Body Fungus

Body Fungus generally occurs when your fish live in negative water conditions, and it involves fungus growing on your fish’s body.


Body Fungus usually only occurs on fish that are already weakened from another type of disease, and they will likely have other infections or parasites if they have Body Fungus.


  • Gray or whitish growths on the fish’s body, fins, and tail
  • Cottony growth
  • Discolorations


Given that they likely have another disease, you should isolate the fish and attempt to figure out what other diseases they could have, based on their other symptoms. Treat accordingly after diagnosing them with a disease (4).

Common Fish Infections


Ich is one of the most common fish diseases, and it involves a protozoan attacking your fish by attaching itself to their gills, fins, and body.


Your fish may develop Ich if there are sudden drops in the water temperature. Not only that, but it may also occur if you introduce infected fish with other healthy fish, since the parasite travels throughout the tank’s water.


  • White spots on the body and gills
  • Clamped fins
  • Labored breathing
  • Loss of appetite


Ich can negatively affect the fish in your aquarium if it’s not caught on and treated quickly, since the parasites reproduce fast. Given that, you should give your fish medication for parasites and turn up the temperature of the tank’s water if your fish are able to withstand that (2).

Prevention and Care Tips

  • Only put fish together if they’re compatible
  • Refrain from overfeeding your fish
  • Don’t let metal come into contact with the tank’s water
  • Disinfect tanks after sick fish have been removed
  • Maintain the tank water’s pH levels, ammonia levels, temperature, and nitrate levels


Overall, whether you’ve had your fish for years or you’re new to taking care of your aquatic critters, all fish risk obtaining a disease, infection, or other type of illness if they’re not cared for properly. That’s why it’s important to take extra caution when caring for your critters. Not only that, but you should also remain watchful and mindful of the certain diseases that your fish has the ability to retrieve.

If you think your fish is showing signs of a disease, contact your veterinarian and conduct the means necessary in order to prevent your fish’s disease from getting worse or causing death. Above all, keep your fish’s tank clean so that your fish can always remain happy and healthy.

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