While aquarists don’t give them as much attention as they should, the cardinalfish (family Apogonidae) are some of the most abundant fish on the coral reef (both in number of species and number of individuals). Many are smaller in size and display dramatic color patterns and bright colors. The yellowstriped cardinalfish (Apogon cyanosoma) is one of a few species in the family that often shows up in the aquarium trade. While many cardinalfish are more active at night, this species also spends most of the daylight hours in the open — a good thing for aquarium viewing!
Difficulty: Apogon cyanosoma is an attractive, durable aquarium fish. If proper microhabitat is provided, the yellowstriped cardinalfish readily acclimates to aquarium life. It normally accepts the more common aquarium foods, such as finely chopped frozen seafood, frozen preparations and even flake foods. Feed the yellowstriped cardinalfish once or twice a day.
Physical description: The yellowstriped cardinalfish is bluish silver overall with six orange-yellow stripes. There are several similar-looking species that differ in the stripe number and/or position. One of the most likely to be encountered by aquarists is the coral cardinalfish (Apogon properupta). This fish has five wider orange stripes on the body. It is known from the Maldives to Indonesia and Papua New Guinea. Many cardinalfish, including the yellowstriped and coral, were formerly placed in the genus Apogon have now been moved into the genus Ostorhinchus.
Range: The yellowstriped cardinalfish is found from the Red Sea east to the western Pacific (from southern Japan south to the Great Barrier Reef). The yellowstriped cardinalfish tends to occur on lagoon patch reefs and coastal fringing reef, where it usually hangs out among stony and soft corals. The known depth range is as shallow as 3 feet to as deep as 160 feet. The yellowstriped cardinalfish is usually found in small to larger groups. Within adult groups, heterosexual pairs can be recognized as they swim close together and display for one another. Juvenile Apogon cyanosoma are sometimes found refuging among the tentacles of the long-tentacled plate coral (Heliofungia actiniformis).
Compatibility: The yellowstriped cardinalfish is a passive fish that will not harm its tankmates, although an occasional large adult may eat a smaller anemone shrimp (Periclimenes spp.) or a nano-goby. Apogon cyanosoma is a likely target of hawkfish, dottybacks, dwarf seabass, damsels, aggressive wrasses and pygmy angelfish. It is also food for moray eels, frogfish, scorpionfish, groupers and snappers. A group of Apogon cyanosoma makes a fascinating addition to the reef aquarium. Add all group members at the same time and provide hiding places for all. If the space is too confining, males may quarrel with one another and will have to be separated.
Aquarium conditions: Provide your yellowstriped cardinalfish with plenty of hiding places, including crevices, overhangs and crevices. A single individual or heterosexual pair can be kept in a nano-reef aquarium (e.g., 10 gallons). Acceptable water parameters for the yellowstriped cardinalfish are: pH of 8.1 to 8.4, specific gravity of 1.019 to 1.025 and a water temperature of 74 to 82 degrees Fahrenheit.
Care considerations: The biggest hurdle to the successful care of Apogon cyanosoma is belligerent tankmates. If the yellowstriped cardinalfish is picked on, it is likely to hide more and eat less. Otherwise, this species is relatively simple to care for long-term.
Breeding: Apogon cyanosoma are thought to hatch as either male or female, with no sex change. All species studied to date orally incubate their eggs. The female yellowstriped cardinalfish releases the egg mass, and then the male takes the eggs into its mouth. The eggs remain in the mouth for about seven days. When the eggs hatch, the male spits the larvae into the water column, where they develop for up to two months before settling out of the plankton. The larvae will need to be removed from the brood stock aquarium (or the adults can be removed). The best first foods for the larvae are rotifers and copepod nauplii.