Because of its small size, domestic rectangular aquariums should not be raised more, but less should not be raised more. For example, in a container with a length of 40 cm, a width of 25 cm and a height of 30 cm, 6 to 8 small goldfish with a length of 5 to 7 cm can be raised. For example, a round glass jar with a diameter of 26 cm and a height of 13 cm can raise 4 ~ 6 small goldfish with a diameter of 4 ~ 6 cm. Adult fish with a body length of more than 8 cm should not be raised in small glass tanks, but in large glass tanks or ceramic tanks, with a small oxygenator for standby to prevent hypoxia. These stocking densities are only reference figures, but also depend on the level of water temperature, the strength of fish and the quality of water, and cannot be determined mechanically. Generally speaking, the fish is big and has a small number of animals. Raise more in winter and less in summer; When the water temperature is low, you can raise more, and when the water temperature is high, you should raise less. Domestic goldfish, if you master the above points, will certainly be able to keep goldfish healthy and lively, colorful, swimming in the water, loved by people, so that you can never get tired of watching it and have fun. I'm sure I can raise it. I wish you success.