Different Types of Fish Diseases

Whether kept in a pond or a tank, captive fish are vulnerable to several types of disease. Wild fish can contract similar illnesses, but the proximity of fish sold as pets and those farmed for food increases the risk of infections spreading. Some diseases are easily treated with simple changes to water conditions or feed. Many diseases, however, pose a serious risk to fish health and can cause death.

  1. Dropsy

    • Dropsy causes bulging eyes and protruding scales, according to the environmental science site Monga Bay. Several factors can trigger dropsy, including bacterial infection or poor water quality. The end result, however, is fluid buildup in the abdomen that can lead to kidney failure, according to the University of Washington. Unfortunately, treatments are not always successful. Since dropsy can be contagious, infected fish should be isolated and treated with antibiotics.

    Velvet Disease

    • Advanced stages of velvet disease, or oodinium, shows on infected fish as a light brown dusty coating. Earlier signs include lethargy, clamped fins, labored breathing, and rubbing against areas of the tank, according to Washington State University. Treatments include using a copper-based solution available from pet and aquarium stores. This solution kills the parasite that causes velvet disease.

    White Spot (Ich)

    • Ich, or--as it is commonly known--white spot disease, is a contagious disease caused by the protozoa Ichthyophthirius multifiliis. Ich is one of the most common fish diseases in aquariums and ponds, particularly among tropical species. Symptoms include rubbing up against objects and gravel, and small pale spots near the gills and on the body. Left untreated, ich is usually fatal. Fish overcrowding can accelerate the spread of the disease.

    Ammonia Poisoning

    • Fish produce ammonia through their waste products. Normally, the amount of ammonia produced is diluted enough not to bother the fish. Ammonia buildup in a fish tank, however, can cause ammonia poisoning. Overfeeding, decaying plants, and rarely changed or poorly filtered water can be root causes, according to Monga Bay. Fish swimming erratically or gasping at the water surface are common signs of ammonia poisoning. Testing water pH can help detect excess amounts, with any reading over 7 indicating too much ammonia.

    Icthyophonus Disease

    • Icthyophonus disease can cause organ damage and spine curvature in infected fish. The fungus icthyophonus hoferi triggers the condition, which can occur in both fresh and salty water, and in captive or wild fish, according to the University of Florida. There is no cure for the disease, but many fish can live with the condition if properly managed and monitored. Methods of prevention include avoiding fresh fish as food for captive fish.