The Comet goldfish is ideal for novice goldfish keepers since it is tough and adaptable and do not require a lot of pampering to do well. It can be kept in outdoor ponds as well as in big cold water aquariums. They can grow quite big as an adult and a length of 14 inches is not uncommon. There exists several different variants of the Comet goldfish, but they all have long and slender bodies and a big and elongated single tail fin. The large tail fin gives the Comet goldfish a very stylish streamlined body shape.

The name Comet is probably derived from how they resemble comets in the sky with long and flowing tails. You can find multicoloured variants as well as specimens with single coloured bodies. One example of a popular Comet goldfish variant is the beautiful Sarasa Comet goldfish. This fish will typically display a multicoloured body and look a bit similar to a Koi fish.

The home of a Comet goldfish should contain densely planted regions as well as big open areas where it can swim around without being entangled in aquatic plants. If you keep your Comet goldfish in an aquarium, you can for instance use Anubias, Crinum, Elodea (Egeria) and Java moss. Keep in mind that many popular aquarium plant species can not tolerate the low temperatures in a goldfish aquarium. In an outdoor pond, you must select aquatic plant species suitable for your particular part of the world and it is therefore difficult to provide any general recommendations. Getting a Comet goldfish to eat is not difficult and they will accept a wide range of different food types, including flakes and pellets. A varied diet is recommended to make sure that your Comet goldfish receives all necessary nutrients.

Vegetables should always be included in the diet and you can for instance feed it lettuce, zucchini and peas. The amount of food must be adjusted according to season, since the metabolism of the Comet goldfish is affected by the water temperature. Feeding your Comet goldfish the same amount of food year round in an outdoor pond that is affected by seasonal temperature variations can result in obesity or starvation. Comet goldfish are not only bred in outdoor ponds; they frequently reproduce in large aquariums as well. They are naturally inclined to spawn in spring when the water gradually becomes warmer and warmer after the winter.

If you do not live in a region where this happens, or if you keep your Comet goldfish indoors, you must usually simulate a winter season and a subsequent spring to coax your fish into spawning. Decrease the water temperature for at least 30 days before you gradually allow it to become warmer and warmer. Professional breeders will often separate the fry from the adult fish to ensure a high fry survival rate.

If you keep your fish in a well planted pond or aquarium where the bottom is covered with large grains, at least a portion of the fry will however survive even when kept with adult fish.

Allen Jesson writes for several sites including two sites that specialize in salt water and fresh water aquariums and the aquarium site and Seapets, a leading source for aquariums and fish tanks.