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Why does my fish have a white growth on its head after coming inside?

Updated On September 23rd, 2025

Pet's info: Fish | Unknown - Fish | 2 years and 10 months old

My fish lived outside during the summer eating alge out of our pond. Now it's inside for the winter but it has developed a white growth on its forehead

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1 Answer

Most Helpful Answer

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Answered By Angel Alvarado, LVT

Licensed Veterinary Technician

Published on November 7th, 2017

Check water chemistry and filtration. Sunny may have developed a bacterial or fungal infection due to the switch in environment. Clean water is crucial to resolving infection. Perform regular partial water changes. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. Maintain water temperature between 75 F and 72 F. Minor infection maybe resolved using plain aquarium salt (NOT table salt). Salt is a great general tonic. It reduces stress, improves gill function and aids in recovery. Dissolve 1 teaspoon of salt per gallon of water in a cup of tank water and gently pour it into the tank. Treat until symptoms resolve. When performing water changes, use just enough salt to treat the water being replaced, not the entire tank volume. If necessary, you can use a broad spectrum medication if symptoms persist. Look in the aquarium section of the local pet or fish store for products such as Kanaplex, Maracyn or Lifeguard by Tetra. Follow label directions carefully and remove the carbon filter insert if indicated.

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