Signs & Symptoms of a Sick Tropical Fish in My Tank

Written by peter mitchell
  • Share
  • Tweet
  • Share
  • Pin
  • Email
Signs & Symptoms of a Sick Tropical Fish in My Tank
Fin rot can damage tropical species such as angel fish (tropical fish image by kenny woodruff from

It's common for some aquarium fish to occasionally get sick. Fish tanks often harbour bacteria and fungal agents, which can cause infection and disease. Tropical fish also become more vulnerable to sickness as they age. However, it's important to keep a keen eye on aquarium fish for signs of illness. This can prevent any diseases or serious conditions spreading to other fish in the tank, and even save the life of the affected fish.

Swimming Motion

One telltale sign of a sick fish is the way they swim. Symptoms of illness can include swimming sideways or rolling to one side. Also, sick fish frequently clamp their fins tight to their body, according to Sick tropical fish may also lay motionless close to the bottom of the tank.

Fin Rot

Fin rot is a fungal or bacterial infection that can seriously damage fish fins. One of the early signs of fin rot is a light fuzz or white substance on fins, according to the Massachusetts Institute of Technology. Other signs include frayed fin edges and more transparent skin on the tail and dorsal fin. Fin rot can spread to other fish, so early treatment is recommended.

Faded Color and Eyes

Many sick aquarium fish, particularly brightly coloured tropical varieties, will fade in colour when sick. Some diseases can also trigger discolouration in tropical fish. Patches or spots may appear on scales and fins. Sick fish may also have faded, cloudy or swollen eyes, according to TropicalFishExpert.


Much like humans, fish often lose their appetite when they feel sick. Signs of a lost appetite in tropical fish might be finding fish food flakes on the surface of the water hours after putting them in the tank. A low appetite may also be a sign of an internal wound or parasite.


Sometimes lesions or wounds on a fish aren't visible to the naked eye. Yet, in cases of infection, sometimes sick fish will rub up against the sides of the tank or the bottom gravel. This is to soothe any itching they may be suffering. Itching can be a sign that the fish will soon develop larger sores, or that they have contracted a virus.

Ich Spots

Ich is a disease caused by a parasitic protozoa. It's very common in fish kept in aquarium tanks. Ich is easily recognised through small white dots on the fish's body and fins, according to MIT. In some cases, fish infected with ich have difficulty breathing and may display faster gills movements or "gasping" motions.

Don't Miss

  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the site, you consent to the use of cookies. For more information, please see our Cookie policy.