White frost on goldfish is caused by saprolegnia or white spot disease. It is usually caused by wounds on the goldfish's surface that lead to infection. The bacteria parasitize on the goldfish's surface, causing hoarfrost to appear on the goldfish's body. Once white frost is found on a goldfish, it must be isolated immediately because saprolegnia or white spot disease is contagious and will be transmitted to other goldfish.

Tip:

When white frost appears on the goldfish, the owner can first use a small brush to brush off the white frost on the goldfish, and then use salt water or add oxytetracycline for medicinal bath and disinfection. Saprolegnia or white spot disease is usually caused by low water temperature, so when treating goldfish, you can increase the water temperature appropriately, and the goldfish will recover in about a week.