[3] Aquarium granuloma presents as a slow-growing, inflamed red bump (nodule or plaque) at the site of infection.

If this condition is acquired from a swimming pool, then symptoms can also develop on trauma-prone body zones, such as the elbows, knees, feet and the tip of the nose.

[7] For the infection to develop in humans, the two main factors required are exposure to contaminated water, and abrasion or injury to the skin.

[3] Lab tests for finding M. marinum include cultures where a swab or sample is taken and grown in the laboratory.

Treatment may still be considered even if the test results are negative, especially if the patient's history supports past fish or fish-tank exposure.

[3] In the absence of positive culture results, a skin or tissue biopsy may be a helpful test to render a microscopic diagnosis.

[4] Surgery may also be needed to remove dead tissue and for excision or debridement if the lesions do not clear with antibiotics.