Koi vs Goldfish: Understanding Their Unique Characteristics and Compatibility

When selecting fish for a backyard pond or water garden, there are several options to choose from with the most popular being koi fish and goldfish. Both varieties have a lot in common but also have some differences. Are koi goldfish? Can koi fish and goldfish live together? Are koi or goldfish better for my pond? Can koi and goldfish breed? Will koi eat goldfish? These are all important questions that need to be addressed prior to adding new fish to your pond.

Are koi goldfish?

No. While koi fish and goldfish both originated from carp, goldfish are much older than koi. Originating over 1,000 years ago, goldfish were first bred in China and are believed to be descendants of Prussian carp or possibly crucian carp, both a lackluster colored fish primarily used as a food source for other fish.  Koi fish raised and sold in the United States today originated in Japan from Amur carp. Amur carp also lack color, but selective breeding introduced the dozens of color and scale patterns available today.

Can koi and goldfish live together?

It depends on your pond size. Goldfish and koi fish do well together under most circumstances. Straight-tailed varieties of goldfish, like comets, sarasa comet goldfish and shubunkins are very compatible with koi fish and will do fine in a pond with koi and butterfly koi. We offer a mix of all these varieties as a great starter pack if you are looking for a variety of fish and colors.

Fancy tailed goldfish like red fantails and calico fantails don’t always do well with koi. If you have a large pond, both varieties co-exist just fine. However, if you have a smaller pond, we recommend not putting fancy tailed goldfish with koi. Fantail goldfish are slower swimmers compared to straight tailed goldfish and koi. Koi can be more playful than goldfish, and will chase the slow swimming fantails, typically picking at them and damaging their tails.

A plus for keeping koi and goldfish, they are both cold water fish and thrive in the same water conditions. You do not need to have a separate set up for the varieties.

Are koi or goldfish better for my pond?

This not only depends on your pond size, but also your budget or new fish for your water garden. Mature goldfish will reach 10 to 12 inches in size, while mature koi fish can reach 30 inches or larger. Ponds 1,000 gallons or larger in size are great for koi, with ponds smaller than 1,000 gallons more suitable for goldfish. If you have a smaller pond and would like a variety of fish and colors, adding fewer koi and more goldfish is a great option.

If you have a larger pond and love the look of koi, you will have plenty of room to add several koi or butterfly koi. Goldfish also excel in larger ponds and would look stunning on their own as well. If budget is a concern, goldfish tend to be more affordable than koi.

Both varieties will be fine on their own and combined.

Can koi and goldfish breed?

Yes. It is possible for Koi fish and goldfish to cross breed. However,  it does not commonly happen as they are not usually spawning at the same time or location. If it does take place their offspring are traditionally sterile, and colors are unappealing.

Will koi eat goldfish?

Yes, koi will eat goldfish under certain circumstances. Mature koi will feast on smaller fish, including mosquito fish and goldfish. However, they typically will only eat immature goldfish that are smaller than one inch in size. You should not experience any issues with koi bothering mature goldfish.

Are you ready to add new koi or goldfish to your backyard pond? Check out our collection of koi, goldfish and other pond critters today.