How Big Can Fair Goldfish Grow?

Those little bowls of cerulean blue water housing golden, aquatic creatures are enticing to a child, which is why so many kids come home with fair fish every summer. A goldfish won at a fair is able to live just as long -- and grow to be just as big -- as a fish from a pet store, if cared for properly.

  1. Lifespan

    • Goldfish start small, but grow throughout their lives.

      Goldfish grow throughout their lives, depending on tank size and food intake. A goldfish lives a few weeks or a few decades, depending on its living conditions. The primary reasons fair goldfish die are poor water quality and limited space. Goldfish produce a lot of waste and need regular water changes and filtration systems to stay healthy. They also need several gallons of water to reach their natural size -- up to 1 foot long.

    Fish Variety

    • Goldfish vary in size depending on the variety.

      Most goldfish given as prizes at fairs are feeder fish, or common goldfish. These fish are usually about 1 inch long to start, but grow to 12 inches or more with enough space. Occasionally, comets or even fancy goldfish are given out as prizes. Comets have longer bodies and smaller, more compact fins than standard goldfish. They are able to grow more than 12 inches long. Fancy goldfish tend to have longer fins, fatter bodies, and distinctive features like bubble eyes or bulbous heads. They often grow wider as well as longer, but also are able to reach 10 to 12 inches in length.

    Tank Size

    • If kept in a pond, ordinary goldfish sometimes reach 12 inches in length.

      Goldfish grow in proportion to how much space they are given. A single fish in a 50-gallon tank grows much larger than a fish spending its entire life in a 10-gallon tank. A 55-gallon tank is recommended for one goldfish to reach its maximum lifespan. A fish in this environment lives a long, healthy life, as much as 20 years or longer. Goldfish kept in smaller tanks die prematurely. Unfortunately, many goldfish in small tanks die because their organs continue to grow while their bodies are stunted, crushing them from the inside out.

    Feeding

    • All animals increase in size based on food intake, even goldfish.

      The growth of the fish is stunted if it is underfed. It is recommended to feed goldfish twice daily, and only as much food as the fish is able to eat in 5 minutes. Proper feeding allows the fish to reach a greater size, as long as it has enough space. Like any animal, fair fish also become overweight from eating too much food while lacking in swimming space.