What Are the Causes of Fish Tank Granuloma?

Fish tank granuloma is a skin disease caused by Mycobacterium marinum, an atypical bacterium that grows in both freshwater and saltwater environments. When human skin is exposed to the bacteria, small bumps, or granulomas, appear on the infected skin. In the United States, fish tank granuloma is rare; 100 to 150 cases are reported annually, or 0.27 cases per 100,000 adults. The condition is treatable with antibiotics, but recovery can take up to 10 months or more.

  1. Infection

    • Fish tank granuloma affects home aquarium owners and people who spend time in saltwater or freshwater. Skin becomes infected when an open wound, such as a scrape or scratch, comes in contact with the waterborne bacteria. People who handle fish regularly or use machinery or sharp tools in aquariums or marine environments are at an increased risk. In the United States, most cases of granuloma can be traced back to a home aquarium, although a few cases involve swimming pools.

    Symptoms

    • The first indication of fish tank granuloma is a red or tan bump on the surface of the skin. Common areas of infection are the hands and arms, which are more likely to come in contact with water in the home aquarium. Over time, granulomas may spread or become sore to the touch. In some cases, granulomas enter the bloodstream and can be felt under the skin.

    Treatment

    • The only cure for fish tank granuloma is a series of antibiotic treatments. Physicians often misdiagnose fish tank granuloma as a skin allergy or rash, which can complicate the infection and recovery rate. Because of the lack of awareness, the average time between initial infection and treatment is usually one year or more. If you suspect fish tank granuloma, inform your doctor about your exposure to saltwater or freshwater.

    Prevention

    • Prevent infection from Mycobacterium marinum by taking precautions when coming in contact with fish or aquarium materials. Wash your hands with antibacterial soap after handling fish or working with your aquarium and its accessories. If you have minor wounds or sores on your hands, wear latex gloves before touching the water in the aquarium or handling fish. Fish tank granuloma cannot be passed from person to person.