What Is Ich (White Spot Disease)?

Ichthyophthirius multifiliis — more commonly known as “Ich” or “white spot disease” — is one of the most common parasites in the aquarium hobby. If you see tiny white dots on your fish that look like grains of salt, chances are, you’re dealing with Ich.

Ich affects both freshwater and saltwater fish, weakening their immune systems, stressing them out, and if left untreated, killing them. But with early detection and the right treatment, Ich is completely curable.

👀 Symptoms of Ich in Aquarium Fish

• Small white spots on body, fins, or gills (like salt or sugar)
• Scratching or “flashing” against decor
• Rapid breathing or gill movement
• Lethargy and loss of appetite
• Clamped fins or hovering in one spot

If you see these symptoms, immediate action is crucial. Learn the basics of aquarium fish health to catch problems early.

🔍 What Causes Ich?

Ich is usually introduced via new fish, plants, or contaminated equipment. It can also lie dormant in your tank and activate when fish are stressed.

• Introducing new fish without quarantine
• Sudden changes in temperature or water chemistry
• Overcrowding or poor water quality

Be sure to follow best practices for first-time aquarists to reduce risk from the start.

🛠️ How to Treat Ich: Step-by-Step

Treating Ich means attacking the parasite in its free-swimming stage — not when it’s embedded in the fish’s skin. That’s why treatment usually lasts 7–14 days.

Step 1: Quarantine If Possible

Move infected fish to a hospital tank if you have one. This prevents reinfection and lets you treat aggressively without affecting plants or invertebrates.

Step 2: Raise the Temperature Gradually

Increase temperature to 82–86°F (28–30°C) to speed up the parasite’s life cycle, making treatment more effective. Raise by 1°F every 6–8 hours to avoid shocking your fish.

Step 3: Begin Treatment

• Medications: Malachite green, formalin, copper, or Ich-X are effective.
• Salt Treatment: Use non-iodized aquarium salt at 1 tablespoon per 3 gallons.
• Remove Carbon: Take out activated carbon from filters before treating.

Step 4: Maintain Clean Water

Perform daily or every-other-day water changes (25–50%) during treatment. Test water regularly using a reliable test kit to ensure optimal parameters.

⏱️ How Long Does Treatment Take?

Typical Ich treatment lasts 7–14 days, depending on temperature and severity. Continue treatment for at least 2–3 days after the last visible white spot is gone.

🚫 How to Prevent Ich Outbreaks

• Always quarantine new fish for 2–4 weeks
• Keep temperature and parameters stable
• Avoid sudden stocking or equipment changes
• Sanitize nets and tools between tanks
• Feed high-quality, varied foods to boost immunity

Prevention is key. Learn more in our upcoming post: “Fish Disease Prevention: A Practical Guide”.

Final Thoughts

Ich is scary, but it doesn’t have to be deadly. With early detection, the right tools, and some patience, your fish can make a full recovery. Bookmark this guide for emergencies and share it with fellow fishkeepers — you never know when Ich will strike.

Next up: Learn how to spot fin rot before it spreads in our next guide, or return to the Aquarium Fish Health Hub.