Marine Ich / Saltwater Ich (Cryptocaryon)
Saltwater equivalent of freshwater ich. Caused by Cryptocaryon irritans. More difficult to treat than freshwater ich.
Check these symptoms in your tankSymptoms of Marine Ich / Saltwater Ich (Cryptocaryon)
- White spots on body/fins
- Scratching against objects (flashing)
- Rapid gill movement / labored breathing
- Fins clamped against body
- Lethargic / hiding more than usual
How to treat Marine Ich / Saltwater Ich (Cryptocaryon)
- Hyposalinity (1.009–1.010 SG) in a hospital tank, never in a reef
- Copper-based treatments (Cupramine): effective but toxic to inverts/corals
- Tank transfer method (TTM): move fish every 3 days to break lifecycle
- UV sterilizer helps reduce free-swimming stages
- Fallow main tank for 8+ weeks while treating
How to prevent it
- Mandatory 4–6 week quarantine for all new fish
- Reduce stress: stable salinity, appropriate flow, hiding spots
Conditions with similar symptoms
The most common aquarium disease. Caused by the parasite Ichthyophthirius multifiliis. Looks like salt grains on the fish's body and fins.
Caused by a dinoflagellate parasite. Appears as a fine gold or rust dust on the fish. Highly contagious and fast-moving, often fatal if not treated immediately.
Includes skin and gill flukes, anchor worms, and fish lice (Argulus). Fish may scratch against objects (flashing) and produce excess mucus. Often introduced with new fish or live food.
Not sure? Use the symptom checker
Many fish diseases look alike. Pick the symptoms you see in the free fish disease checker to compare likely causes, or scan a test strip to rule out a water problem first.