Keeping tropical fish can be a very rewarding and relatively easy and inexpensive hobby. It is extremely relaxing for most aquarium owners to sit and watch their fish swimming around. It is also very entertaining to watch their antics and eventually learn their habits and even personalities. Like any beloved pet, if your fish shows signs of illness, it can be very distressing for you as the owner.

Most fish diseases can be classified as:

  • Bacterial Infections: Common symptoms are cloudy or bulging eyes, open sores or skin inflammation, color loss, and frayed fins.
  • Fungal Infections: If your fish has cotton-looking tufts around the eyes and mouth or on the skin itself and seems to be swimming erratically, it could be a symptom of a fungal infection. 
  • Parasitic Infections: Symptoms of parasitic infections include slime or mucous on body, inactivity, difficulty breathing, visible dots or worms on the skin, or scratching up against tank ornaments.

Here are three common ailments to be aware of and the steps you can take to alleviate them.

Body Flukes and Gill Flukes


This parasite will present as reddened skin, a mucous coating, rapidly moving gills, scratching, and a chewed up appearance to the gills or fins.

Causes: Flukes are caused by an inhospitable aquarium. This could be poor water quality, species incompatibility, or overcrowding.

Cure: Use a commercial aquarium medication for parasites. Make sure it has the ingredient praziquantel in it. Use as directed, and in between treatments, do partial water changes.


Symptoms: The fish will look bloated and its scales will have a raised appearance, as though they were projecting from the body.

Causes: Dropsy is caused by a bacterial infection of the kidneys. This causes the bloating and may lead to complete renal failure. While it is more common in fish with a suppressed immune system, it can also be caused by a dirty tank.

Cure: Treatment can be challenging so preventative care is best. Be sure to clean the tank regularly, taking care to maintain the proper chemistry. The addition of aquarium salt may also help. Feed medicated antibiotic flake food exclusively for 10 days.


Symptoms: The initial symptoms are patches of gray or white areas on the skin. As the fungus grows, it will become like a cottony growth growing from the fish. If left untreated, the fungus will continue to basically eat the skin and the fish will die.

Causes: Fungus typically appear as a secondary infection in a stressed fish who is already ill or was physically attacked by another fish.

Cure: Use a commercial aquarium fish fungal treatment. Because bacterial and fungal infections can overlap, feed medicated antibiotic flake food as well. Half-way through treatment, start partial water changes. 

For more information about caring for your tropical fish, contact a business such as Congressional Aquarium