Can You Mix Goldfish & Guppies in the Same Aquarium?

Guppies and goldfish are two of the most popular species of aquarium fish. Both goldfish and guppies are colourful fish that are relatively easy for which to care. Despite being peaceful community fish, goldfish and guppies have different needs and tank requirements that make it inadvisable for them to be kept in a tank together.


When selecting fish for a fish tank, it is important to determine whether the species are compatible. Aquarium fish are described as aggressive, semi-aggressive or community fish. Both guppies and goldfish are community fish that do well in groups of their own species and with other peaceful species of fish. Though they do not show aggression toward each other, there are other factors that make goldfish and guppies incompatible tank mates.

Fish Size

When determining whether it is safe to mix certain species of fish, consider the potential size of both species. In general, large fish tend to eat smaller fish. Guppies only grow to a maximum size of 2 inches and goldfish grow to be quite large. With this being true, large goldfish are almost expected to eat guppies if they are placed in a tank together. There are other factors besides size that are also taken into consideration.

Tank Requirements

Guppies are known for being hardy fish that are great for beginner tanks. Guppies are capable of tolerating varying water temperatures and do not require a great deal of space. Goldfish, on the other hand, require at least 20 gallons of water volume and excellent filtration because they have a high waste output. The waste output of goldfish tends to lead to a quick build-up of ammonia and nitrates, which is harmful to guppies if they are kept in the same tank.

Water Temperature

Aquarium fish are generally divided into two different groups by the type of environment in which they live, saltwater and freshwater. These groups are further divided by water temperature, tropical or cold water. Goldfish and koi are cold water fish, which makes them ideal for use in outdoor ponds. Guppies, though able to survive in cooler temperatures, are tropical fish and thrive best in water between 23.9 and 26.7 degrees Celsius. Because of these differences, goldfish and guppies are not to be kept together.

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About the Author

Katherine Barrington has written on a variety of topics, from arts and crafts to pets, health and do-it-yourself projects. She has a Bachelor of Arts in English with a creative writing concentration from Marietta College.