What Is The Difference Between A Comet And A Common Goldfish?

If you want to add a comet or common to your new fish tank but can’t tell the difference between the two. Both the common and the comet goldfish are great options for living in ponds or for beginners.

Here are some physical differences to look out for that will help you determine which is which.

A Comet Goldfish.
Comet Goldfish

The Different Fins And Tails

Common goldfish have shorter fins and tails that appear more rounded.

Comet goldfish have longer flowing tails and fins that appear pointier than the common goldfish.

When these two fish are younger, they are easier to tell apart as the comet goldfish will have a longer, slimmer body and a deeper forked tail.

Color And Size Differences

Although these fish are very similar in color, the common goldfish will usually have more iridescent colors and could include darker colors and grey tones. The common goldfish is the more elongated and oval-shaped fish.

The comet is identified as the shorter, leaner fish with more of a two-toned red-and-white combination or reddish-orange color.


Both common and comet goldfish are sold as feeder fish or at carnivals as prizes, and unfortunately, little attention is paid to their breeding standards. Feeder fish are usually smaller kinds that aren’t expensive and, as their name suggests, become food for other fish or aquatic animals.

Both the comet and the common goldfish are easy to breed. The fish reach their sexual maturity around a year, so after a year, you can expect spawning to occur depending on when you get your fish.

Once the spawning has started, removing the eggs and placing them in a separate tank is best. When he is ready to start breeding, you will see white spots on the male fish. The white spots are called breeding starts and mainly form on his gills, bottom fins, or scales.

You can easily identify who is male or female when you look at the fish from a top view. The female fish usually have a rounder, fatter body. When they carry their eggs, they do so on the sides of their tummies, which extenuates their rounder tummies even more.

Habitat And Lifespan

Due to the size of a fully grown common goldfish (18 inches or 45cm), they strive in a larger tank or outside pond.

The lifespan of the common goldfish can go all the way up to 20 years depending on their living conditions, luckily these fish are very hardy but care should be taken to give them enough space to grow and live a good life.

The same goes for the comet goldfish, they require a lot of space and will flourish in larger longer tanks and outdoor ponds.

A fully grown comet (12 inches or 30cm) is known to be an aggressive feeder, so longer tanks and larger ponds assist as you can deposit food in multiple areas of the space to assist with this issue.

Common Goldfish
Common Goldfish


Goldfish pellets and flakes are great as the staple diet for the comet and the common. Keeping your fish in a pond is even better, as they can supplement their diet with natural algae and plants in their habitat.

You can also add treats for your tank fish, such as frozen brine, shrimp, and bloodworms.

Adding plants that they love to nibble on to your tank for the comets or common goldfish would be a great idea to help them with their dietary needs. Please make sure to leave enough room for these agile swimmers. Duckweed would be a great option to add to your pond or tank.


Although comets and common goldfish have many similarities, there are key physical distinctions that can help you differentiate between the two.

These fish are great options for enthusiasts at all levels, and with the right amount of space and a well-balanced diet, they can provide you with years of enjoyment.

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