Furazolidone has little toxicity to fish and turtles. It can be used for prevention and treatment of early diseases in freshwater fisheries. When the water temperature is below 20 C, soak for 20 - 30 minutes; when the water temperature is above 20 C, soak for 10 - 15 minutes. When the water temperature is about 20 C, the concentration of furazolidone is 0.025 ppm, which can inhibit all kinds of pathogenic bacteria. Goldfish and tropical fish raised in ponds and tanks can tolerate the concentration of 1.5 ppm and will not die. Therefore, in case of serious illness, the concentration of 0.4-1.0 ppm can be used. After spraying drugs throughout the pond, the domestic fish should feed more high-quality commercial feed. Ornamental fish must feed live water fleas, cyclops, chironomid larvae, earthworms and other animal food to strengthen the nutrition of diseased fish and enhance the disease resistance of diseased fish. To prevent white head and white mouth disease, gill rot disease, printing disease, vertical squamous cell disease, erythroderma of domestic fish, soak once before stocking. To prevent ornamental fish from white-headed and white-mouthed disease, gill rot, vertical squamous disease, fin rot and tail rot, they are reared in small waters and soaked once a day and again every other day. Treatment of ornamental fish white-headed white mouth disease, gill rot disease, vertical squamous disease, fin rot tail disease, etc., once a day, every other day and once again, can be continuously soaked 3 to 5 times, until the symptoms disappear, the fish body recovers.
However, furazolidone residues can cause potential harm to human beings, such as hemolytic anemia, polyneuritis, eye damage and acute liver necrosis.