Marine Ich (Cryptocaryon)
Cryptocaryon irritans
High severity ⚠️ Contagious
the saltwater version of white spot, a marine parasite needing quarantine treatment away from corals
Symptoms
Catching illness early gives the best chance of recovery, so check your fish daily. Tiny white spots on the body, fins and gills of marine fish, flashing, rapid breathing, clamped fins and loss of appetite. The saltwater equivalent of freshwater white spot. Act promptly if you see several signs together.
Causes
A marine parasite that explodes in numbers when fish are stressed by poor water quality, shipping or unstable salinity; it spreads rapidly through a reef tank. The underlying trigger is almost always stress, poor water quality or a newly introduced animal.
Treatment
Treat in a separate quarantine tank with copper-based medication or hyposalinity (corals and inverts cannot tolerate copper), maintaining the full treatment period. Improve water quality and reduce stress.
While treating, increase aeration, remove activated carbon from the filter, finish the full course even after symptoms fade, and keep the water immaculate. Marine treatments belong in a separate quarantine tank, never the reef.
Prevention
Quarantine all new marine fish for several weeks, keep salinity and water quality rock-stable, and minimise stress. The golden rules: quarantine new arrivals, never overstock or overfeed, avoid sudden swings, and keep up regular water changes.
FAQ
What is Marine Ich (Cryptocaryon) in fish?
How serious is Marine Ich (Cryptocaryon)?
How do I treat Marine Ich (Cryptocaryon)?
Can Marine Ich (Cryptocaryon) be prevented?
Will it spread to my other fish?
This information is general guidance, not veterinary advice. Consult an aquatic vet for serious cases.