Koi Vs. Goldfish Differences

Both koi and goldfish are a species of carp and members of the minnow family, or Cyprinidae. Both types of fish are attractive with vibrant coloring, which makes them a common addition to ponds and water gardens. Despite certain similarities in color, however, koi and goldfish are not the same and have both visible and unseen differences between them.

  1. Appearance

    • When it comes to the appearance of koi and goldfish, there are several noticeable differences in size and shape. Koi have elongated bodies and are the larger of the two fish, usually 18 to 24 inches long, although they do have the potential to grow to 4 feet. At the koi's mouth are a pairs of whisker-like feelers that are known as barbels. These are sensory organs that are not found on goldfish. Depending on the variety of goldfish, their bodies tend to be more rounded and shorter than koi and they can grow to be from 8 to 14 inches or larger. Although the two fish come with similar coloring, the color markings are often larger on koi.

    Pond Life

    • Due to their large size, koi do best in ponds that are 500 gallons or larger and they require a filtration system for maximum health. Care should be taken when adding plants to a koi pond, as koi are generally rough on plants and will chew and uproot them, plus they will disturb potted aquatic plants. Goldfish benefit from plants, and rarely if ever cause damage to them. Goldfish do well in smaller garden ponds and require no filtration system unless there are a large number of fish in the pond. However, during 75 degrees or hotter weather, aeration is beneficial to help circulate the water and prevent the fish from becoming stressed.

    Cost

    • Goldfish are available for purchase at most pet and aquarium stores and even certain garden centers. They are relatively inexpensive in comparison to koi, which can cost hundreds of dollars depending on a variety of factors such as breeding and coloring.

    Lifespan

    • Both goldfish and koi can have relatively long lifespans, however, of the two koi are generally longer lived. You can expect goldfish to live up to 30 years when kept in the right conditions and away from predators. According to the Southern Regional Aquaculture Center, healthy koi can live for approximately 50 years.