Ich (white spot disease)
White spots like grains of salt.
Raised white dots the size of salt grains on the body and fins, often with flashing (rubbing on decor) and fast breathing. It is a parasite, Ichthyophthirius multifiliis, and it spreads to every fish in the tank.
- Do this first
- Confirm it is ich before you treat: other problems can look like white spots, and a vet confirms ich by looking at a skin scrape under a microscope.
- Call a vet when
- Call a fish vet if fish keep dying, the spots return after a full course, or you keep sensitive species such as loaches or shrimp that some treatments harm.
On a real fish: white spots (ich) on a cardinal tetra. Photo: D. Herdemerten Hannibal21, CC BY 3.0, via Wikimedia Commons
Likely causes
- New fish added without quarantine
- Stress from a temperature drop or poor water
- Clown loaches, tetras and other scaleless or small fish catch it first
What to do today
- Confirm it is ich before you treat: other problems can look like white spots, and a vet confirms ich by looking at a skin scrape under a microscope.
- Then treat the whole tank, not one fish: every fish has been exposed.
- Use an ich treatment sold for aquariums exactly as its label says, for the full course; the spots you see are one stage, and the treatment works on the free-swimming stage that follows.
- Remove activated carbon from the filter while treating, since it takes medicine out of the water.
- Keep the temperature steady and the water clean; test ammonia and nitrite.
When to call a vet
Call a fish vet if fish keep dying, the spots return after a full course, or you keep sensitive species such as loaches or shrimp that some treatments harm. A vet who treats fish can examine it and prescribe treatment; your local fish store or aquarium society can often recommend one.
Stop it happening again
Quarantine every new fish for at least 30 days before it joins the tank. How to set up a quarantine tank.
Sources: Merck Veterinary Manual: Management of aquarium fish; Merck Veterinary Manual: Disorders and diseases of fish; UF/IFAS: Ammonia in Aquatic Systems.