What is a Cardinalfish?

J.L. Drede
J.L. Drede

Cardinalfish are a type of fish in the Perciformes order, making up all the fish in the Apogonidae family. There are many different species of the fish, and many of the smaller species are popular aquarium fish because of their bright coloration and fins. Some of the most popular species include the banggai cardinalfish, the blue-streak cardinal, and the spotted cardinal.

These fish are found in the Atlantic, Indian, and Pacific Oceans. Species of the fish are also found in some freshwater streams in tropical islands. Many species of the fish are from Indonesia, including the banggai cardinalfish, which gets its name from an island of Indonesia.

In the ocean, cardinalfish are typically shallow swimmers, rarely going much below 300 feet (approximately 100 m) and sticking close to the shore. It feeds at night, foraging at the bottom for zooplankton and small invertebrates like as crustaceans. Some will feed on other types of fish as well, but those fish must be small, as the cardinalfish is itself a fairly small species of fish. Most only grow to a maximum length of 4 inches (10 cm), although some can grow to double that length. All species of the fish are known for their very large fins, which can sometimes be as long as the fish's body, and large eyes.

The cardinalfish's small size and peaceful nature have both made it a popular fish for saltwater aquarium enthusiasts. Since it can endure a good variety of water conditions, some fish stores recommend certain breeds of the fish, such as the banggai, as ideal starter fish for those starting a saltwater aquarium.

Aquarium water for this type of fish should have a pH between 8.1 and 8.4 and a hardness of about 8 to 12 degrees Fahrenheit (-13 to -11 Celsius). The temperature of the water can vary between 75 to 82 degrees Fahrenheit (23 to 27 Celsius), while the specific gravity can be between 1.023 and 1.025. The fish is carnivorous in the wild, so it should be fed frozen foods or even some live foods. After it becomes accustomed to eating in the aquarium, it may also eat flakes on occasion as well.

Cardinalfish swim in schools in the wild, so they should be kept in at least groups of two or three. With other tank mates, conditions are usually peaceful as long as the cardinalfish is not significantly larger than other fish in the aquarium. If so, it might view them as food. Aquarium owners say that the fish is also compatible with reef tanks and will not go after snails or anemones kept on a reef.

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