Ich, or ichthyophthirius multifiliis, is one of the most common freshwater fish diseases. It appears as tiny white salt-like spots on the body, fins, and gills, and fish often flash against objects or clamp their fins.

Treatment works best when you understand the parasite's life cycle. The visible white spots are the feeding stage embedded in the fish's skin and cannot be killed by medication at that point. When the parasite drops off to reproduce on the substrate, the free-swimming offspring are vulnerable to treatment. This cycle takes roughly three to seven days depending on temperature.

Raising the temperature gradually to 82-86 degrees Fahrenheit, if your fish species can tolerate it, speeds up the life cycle so medication can kill the free-swimming stage faster. Increase aeration because warmer water holds less oxygen.

For treatment, you have several options. Aquarium salt at one tablespoon per five gallons works for salt-tolerant species but harms scaleless fish like loaches and many catfish. Commercial ich medications containing malachite green or formalin are effective for most community tanks. Follow dosing instructions precisely and remove activated carbon from your filter, as it absorbs medication.

Continue treatment for at least three days after the last visible spot disappears to catch any remaining parasites completing their cycle. Perform partial water changes between doses as directed by the medication instructions.

Prevention is the best medicine. Quarantine new fish for two to four weeks before adding them to your display tank. Maintain stable water quality and avoid temperature drops, which stress fish and trigger outbreaks. A well-maintained tank with healthy, unstressed fish rarely experiences ich even when exposed to the parasite.