Chemicals That Treat Ick in Fish

Fish are susceptible to a condition called ick (or ich). It comes from the parasite Ichthyophthirius multifiliis, and causes white nodules to form on the fins and bodies of infected fish. Fish with advanced stages of ick scratch themselves on gravel and other fish tank or pond decorations in search of relief. If even one fish has ick, the entire tank or pond must be treated.

  1. Formalin

    • Formalin for fish is a solution of water with 37 percent formaldehyde gas and 10 or 15 percent methanol dissolved within it. The book, "Fish Disease: Diagnosis and Treatment," recommends three formalin treatments on alternating days at a tank temperature between 24 and 26 degrees Celsius.

    Salt

    • Salt acts as both an ick cure and an ick preventative, according to "Fish Disease: Diagnosis and Treatment." A typical dosage is 1 tbsp. per gallon of water. Before using salt as an ick treatment, make sure it's an appropriate choice for your species of fish.

    Copper Sulfate

    • Copper sulfate is best for freshwater ponds rather than fish tanks. It can be tricky to use correctly without unwanted side effects, so be sure to check the recommended dosage for the solution you buy. At higher temperatures, "Fish Disease: Diagnosis and Treatment" recommends treating ick with copper sulfate every other day at least three times. At lower temperatures, the Ichthyophthirius parasite has a longer life cycle, so you will need to extend treatment.

    Malachite Green

    • Malachite green is good for treating everything from ick to fungus. It can be combined with formalin for a powerful ick treatment. However, it's not recommended for use in tanks with young or newborn fish. Malachite green is a highly toxic chemical and should be handled carefully. Never use it if pregnant, and be sure to wear gloves and a mask while working with it.