Aquarium granuloma

Aquarium granuloma


A swimming pool granuloma is a chronic skin infection caused by the bacteria Mycobacterium marinum.

Alternative Names

Aquarium granuloma; Fishtank granuloma


A swimming pool granuloma results when water containing an infectious organism, Mycobacterium marinum, enters a break in the skin. A localized infection called a granuloma results after about 3 weeks.


The person usually has a history of exposure to swimming pools, salt water aquarium, or ocean fish.

The lesions appear as reddish bumps (papules) that slowly grow into purplish nodules.

The elbows, fingers, back of the hands, and knees are the most common sites affected. The nodules may break down and leave an open sore, or spread up the limb.

Exams and Tests

A skin biopsy and culture is usually needed to confirm the diagnosis. A PPD tuberculin skin test will usually be positive.


Antibiotics are used to treat this infection. Several months of treatment are often needed.

Outlook (Prognosis)

Swimming pool granulomas can usually be treated completely with antibiotics.

Possible Complications

Occasionally, joint or bone infections occur. Patients with defective immune systems may also have longer or more complicated cases.

When to Contact a Medical Professional

Call your health care provider if you develop reddish bumps on your skin which do not clear with home treatment.


Avoid contact with contaminated water. Wear gloves or wash thoroughly when cleaning aquariums.

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