How about raising black goldfish?

The problem lies in the color. Goldfish can't stand the sharp change of water temperature. Be careful not to pour fresh water directly when changing water, and then pour it after an hour of constant temperature. Because the temperature difference of water is 1 to 2 degrees, there will be no big problem, and 3 degrees will cause fish to get sick and dim. If it exceeds 3 degrees, it will die. Black is sensitive to temperature, so it is weak.

Goldfish is an ornamental fish that our people are happy to raise. It has become a natural and living work of art because of its peculiar posture and gorgeous colors, so it is loved by people. According to historical records and modern scientific experiments, scientists have found out that goldfish originated from wild crucian carp, which is widely eaten in China. First, it changed from silver-gray wild crucian carp to red-yellow golden crucian carp, and then from red-yellow golden crucian carp to different varieties of goldfish after domestic rearing in different periods. As an ornamental fish, red crucian carp was recorded in China as early as the Jin Dynasty (265-420). Red and yellow crucian carp began to appear in the "release pond" in the Tang Dynasty, and golden crucian carp began to appear in the Song Dynasty. People began to raise goldfish in ponds, and the color of goldfish appeared in white flowers and spots. In the Ming Dynasty, goldfish moved into a fish tank. In animal taxonomy, it belongs to vertebrates, cephalopods, jaws, fishes, eustoma, CYPRINIDAE, CYPRINIDAE and Carassius. Goldfish and crucian carp belong to the same species and have the same scientific name (Carassius auratus) in science.