How to Kill Ich Using Temperature

Updated February 21, 2017

Ich is a common disease that attacks pet fish. The disease is highly contagious and can kill every fish in a tank, if not treated early. Ich is also known as "white spot disease" because of the white blister-like lesions on the fish. Temperature is used to kill Ich because the cysts, called tomites, that infect the fish will not survive in high temperatures. By raising and lowering the temperature of the aquarium, the Ich will be fully removed from the tank.

Raise the temperature in the tank by turning up the heater a couple of degrees. After a couple of hours, raise the temperature a few more degrees. Keep doing this until the temperature of the water is 30 degrees C. It may be necessary to set the heater at 30.6 degrees C or 31.1 degrees C. What is important is that the temperature of the water is at 30 degrees C or a little higher. Raising the temperature gradually will prevent the fish from becoming stressed.

Keep the temperature of the water at 30 degrees Cor 24 hours. After a couple of hours, lower the temperature a few degrees. Keep lowering the temperature, until it is back to the normal setting your fish require. Keep the temperature at that setting for 48 hours.

Repeat Steps 2 and 3 for 14 days. When the temperature is at 30 degrees C or higher, the heat kills the Ich cysts that want to reproduce. The heat does not kill the parasites that are already attached to the fish. When the temperature is lowered, the parasites ready cysts to reproduce. When the parasite dies, usually after 5 days, it drops off the fish and the cysts are dispersed to find a host. The cysts are killed when the heat is turned up. Repeating the routine kills any cysts that are dispersed, preventing more infections.


Warm water has less oxygen. Add an air stone to help circulate oxygen or lower the water in the tank. The lower amount of oxygen might stress the fish.


Do not use this treatment with cold water fish, such as goldfish. They can't tolerate the high temperature and will die. Many commercial chemicals are sold as cure-alls for Ich, but these chemicals also kill the good bacteria in the tank, may harm scaleless fish and do not always work. Salt is often used to kill Ich, as well. However, it can harm scaleless fish and does not always work.

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About the Author

Marilla Mulwane has been writing professionally since 2005. She has published a fantasy novel for young adults and writes articles on literature, pets, video games and tattoos. Her poetry has been featured on the website and products for the nonprofit organization HALos. She graduated from the State University of New York, Oneonta with a Bachelor of Arts in English and creative writing.