Quick referenceFish pox (lymphocystis) is a viral skin disease causing white-grey nodules on fins + body. Generally non-lethal; nodules regress in 4-6 weeks of clean water + reduced stress.
Symptoms
White cauliflower-like nodules
Lumps on fins + body
No behavior change
Slow growth (weeks)
Gradual regression with care
Cause
Lymphocystis virus (lymphocystivirus). Common in marine fish + some FW species. Stress + poor water quality trigger latent infection. Self-limiting in healthy fish.
Treatment options
No medication needed. Lymphocystis is viral; antibiotics + parasiticides do not help. Clean water + good nutrition let immune system clear it.
Improve water quality. Reduce stress: stable params, no aggressive tankmates, ammonia 0, nitrate <30. Vary diet.
Avoid manual removal. Picking off nodules opens secondary infection routes. Let them regress naturally over 4-6 weeks.
Quarantine new fish. Lymphocystis is contagious to immunocompromised tankmates. Isolate severely-affected fish.
Always treat in a separate quarantine or hospital tank.
Prevention
Quarantine new fish. Maintain stable parameters. Vary diet for full vitamin profile. Avoid stressful aggressive tankmates.
Fatality + outcome
Almost never lethal. Can be temporarily disfiguring; resolves on its own in healthy fish.