Looking at the photo effect, I think they are all grass goldfish, also called golden crucian carp, which is a very common cold water ornamental fish. It is sold in aquarium markets all over the country, and the price is cheap.

The individual size of grass goldfish has a great relationship with the growth environment. The fish grows slowly when the water body is small and the density is high. Therefore, these fish are not counted as adults according to how many centimeters they are long. Usually, after growing for one year, you can reach sexual maturity, which means you are an adult. Generally, adults can reach more than ten centimeters long.