Marine Ich (Cryptocaryon) guide for aquarists. Symptoms, treatment protocol, prevention, and when to escalate.
Marine Ich (Cryptocaryon) TL;DR
Affects: saltwater fish · Symptoms: white spots on body and fins, scratching against rocks, rapid breathing
Treatment:Cupramine copper treatment 21 days, or tank-transfer method (12 days)
What is marine ich (cryptocaryon)
Marine Ich (Cryptocaryon) is a common aquarium disease/pest affecting saltwater fish. Recognizing it early and treating quickly is the difference between losing a single fish and losing an entire tank.
Symptoms to watch for
white spots on body and fins, scratching against rocks, rapid breathing. Watch for behavior changes (reclusive, refusing food, color loss) as early warning signs - even before visible symptoms appear, fish stress patterns indicate something is wrong.
Treatment protocol
Cupramine copper treatment 21 days, or tank-transfer method (12 days). Always treat in a separate hospital tank to protect invertebrates, coral, and beneficial bacteria. Follow medication protocol exactly - underdosing produces resistance, overdosing creates new problems.
Prevention
Quarantine new fish for 4-6 weeks before adding to your display tank. Stable parameters + appropriate stocking + adequate filtration prevent the chronic stress that makes fish susceptible to disease in the first place.
When to escalate
If symptoms persist beyond expected treatment duration, parasites/symptoms reappear after treatment, or the disease spreads despite isolation, escalate to a fish-specific veterinarian or experienced reef keeper. Aquatic veterinarians offer prescription medications (chloroquine, levamisole) not available over-the-counter.
Marine Ich (Cryptocaryon) FAQ
Is marine ich (cryptocaryon) contagious?
Yes - most fish diseases spread via water column or direct contact. Isolate infected fish in a hospital tank.
Can I treat in the display tank?
For most diseases - no. Copper kills inverts, antibiotics destroy beneficial bacteria. Always treat in a hospital tank.