Mycobacterium marinum is an atypical mycobacterium found in both salt and fresh water. It occasionally causes soft tissue infections after minor trauma, principally affecting the limbs.

A 17-year-old male aquarium worker presented with preseptal cellulitis of his right eye, after attempting to lance a hordeolum some days previously. The condition failed to respond to antibiotics and a necrotic area developed, which subsequently required debridement. Histology of the debrided area demonstrated granulomatous inflammation which when considered with his occupation led to the diagnosis of Mycobacterium marinum – ‘fish-tank granuloma’.

A Medline search did not demonstrate any previous cases of Mycobacterium marinum infection occurring peri-orbitally. The current literature regarding diagnosis and management is reviewed. Although infection with Mycobacterium marinum is rare in the general population, this case demonstrates the importance of considering the diagnosis when dealing with patients frequently exposed to fresh or salt water.