Ich shows up as small white dots, like grains of salt, on a fish's body and fins. It is a common parasite that often follows stress or a sudden temperature drop. It is usually treatable if caught early; follow the instructions of an ich treatment made for aquariums, and ask a vet or an experienced fish store if you are unsure.
TankCoach is not veterinary advice. If fish are getting worse, contact an aquatic vet or an experienced fish store.
How to recognise it
White dotsLike salt grains, on body and fins
FlashingFish rub against decor or gravel
Clamped finsFins held tight, less active
Why it happens
Ich is often already present and takes hold when fish are stressed: a cold night, a big temperature swing, poor water quality, or new fish added without quarantine.
General steps
- Test the water. Fix ammonia, nitrite or temperature problems first.
- Treat the whole tank with a product made for ich, following its label exactly. Remove carbon from the filter if the label says so.
- Finish the full course, even after the spots are gone: the parasite has a free-swimming stage you can't see.
- Quarantine new fish next time, for a couple of weeks in a separate tank.
Questions
Is ich contagious?
Yes. It spreads through the water to every fish in the tank, so treat the whole tank, not just the spotted fish.
Can I use salt or heat?
Some keepers raise the temperature gradually or use aquarium salt, but not every fish, shrimp or plant tolerates them. Check what is in your tank before trying either, and when in doubt ask a vet.
General information, not veterinary advice. Updated November 2026.