Generally, when the body length is almost 4-5 cm, you can start (not counting the tail), and there will be some differences according to the variety and nutritional status.
In fact, the growth and development of fish is related to the size of the waters in which they live. The better the water quality, the bigger the area, and the bigger the fish are compared with the same kind, and the smaller the fish are. It has been raised for a long time now, and the fish should have been shaped, so it is not easy to grow again, but now you provide more space, and maybe it will grow again.