Goldfish fry are in the seedling stage within 15 days, 50 days in the seedling stage and 0/00 days in the middle stage. The rule of changing water for fry is not to be too diligent when young, and gradually increase the number of water changes. Just before breaking the shell, replenish fresh water and oxygen content, and try not to change water for 10 days to prevent the residual fish from being injured. In the future, with the increase of food intake and fry, it is necessary to increase the number of water changes. It is best to change the water at 2 ~ 3 pm when the water temperature is the highest, and bask for more than 5 days in advance. First, keep the water temperature consistent; The second is to discharge additives from tap water. Every time you change the water in the fish tank, you should try to disturb the fish as little as possible. Use a plastic hose to suck out the impurities in the bathtub by siphon principle, and slowly add water.