Why dont goldfish grow very big?

Goldfish can actually grow quite large, but the size they reach depends on several factors, including their genetics, diet, and environment.

Genetics

Some goldfish varieties are naturally smaller than others. For example, the common goldfish (Carassius auratus) typically reaches a maximum length of about 12 inches, while the jumbo goldfish (Carassius auratus auratus) can grow up to 24 inches long.

Diet

A goldfish's diet plays a significant role in its growth. A diet that is high in protein and low in carbohydrates will help a goldfish reach its full potential size. On the other hand, a diet that is high in carbohydrates and low in protein can stunt a goldfish's growth.

Environment

The environment in which a goldfish lives can also affect its growth. Goldfish need a spacious aquarium with plenty of swimming room. They also need clean, well-oxygenated water. A lack of space or poor water quality can stunt a goldfish's growth.

In addition to these factors, goldfish may also grow slower if they are kept in a crowded tank or if they are exposed to stress.

With proper care, a goldfish can live for many years and reach its full potential size.