Ich (ick): what it is, what it looks like, and how to treat it

What is ich?

Ich (short for Ichthyophthirius multifiliis), often spelled “ick,” is a parasitic infection. The parasite burrows into the fish’s skin and gills, causing the classic white spots. It has a life cycle that includes a free‑swimming stage, which is when treatments are most effective. Stress, poor water quality, or new fish can trigger an outbreak.

What does ich look like?

Fish with ich typically show small white spots (like grains of salt or sugar) on the body, fins, and gills. They may flick or rub against decor (flashing), breathe fast, clamp fins, or hide. In severe cases you’ll see many spots and the fish can become lethargic or stop eating. If you see these signs, check your water parameters and start treatment promptly.

How to treat ich

Most aquarists combine a few approaches:

• Raise temperature (if your fish tolerate it): Slowly increasing temp to around 78–80 °F can speed up the parasite’s life cycle so it leaves the fish sooner and is exposed to treatment in the water. Do not exceed what your species can handle.
• Medication: Use an ich treatment from your fish store (e.g. containing formalin/malachite green or similar, or aquarium salt where appropriate). Follow the label and remove chemical filtration (e.g. carbon) during treatment. Treat for the full course even after spots disappear.
• Salt (freshwater): Some keepers use low-dose aquarium salt to support fish and mildly stress the parasite. Not all fish or plants tolerate salt — research your stock first.
• Water quality: Keep ammonia and nitrite at zero and nitrate low. Good filtration and a partial water change before or during treatment help. Track your parameters with a log or fish tank app like App-aquatic so you can stay consistent.

Quarantine new fish before adding them to your main tank to reduce the chance of introducing ich. Once you know what to look for and how to treat it, ich is manageable.

Quick takeaways

• Ich (ick) = white spots on fish; flashing and heavy breathing are common signs.
• Treat with medication (full course), optional heat and/or salt where safe, and excellent water quality.
• Quarantine new fish to help prevent outbreaks.