The Black Striped Cardinalfish (Ostorhinchus nigrofasciatus) is a small member of the Apogonidae family, recognized by its pale body crossed lengthwise by bold black stripes, an oversized eye, and the small terminal mouth characteristic of cardinalfishes. The species ranges widely across the Indo-Pacific, with populations reported from Indonesia, the Philippines, Papua New Guinea, the Solomon Islands, Micronesia, and northern Australia. In nature it occupies sheltered water: reef flats, shallow lagoon reefs, coral-rich bays, and protected reef slopes, where it is most often encountered singly or in pairs tucked beneath ledges and inside crevices. Reported maximum size varies between roughly 3 inches and just under 4 inches, so plan for a fish that stays compact at maturity.

Recreate that sheltered habitat with generous rockwork that provides caves, overhangs, and shaded crevices for daytime retreat, along with branching coral structure the fish can hover beside. Low to moderate water movement suits its habit of holding position in the water column rather than fighting current, and standard reef lighting causes no trouble so long as shaded refuges remain available. Published tank recommendations differ considerably, from about 30 gallons at the low end to roughly 132 gallons at the high end, so err toward the larger footprint if you intend to keep a group. Because this is a shy, nocturnal fish, it settles in best in a mature, established system with abundant hiding places and calm neighbors.

This is a carnivore that hunts after dark, emerging from shelter during low light to take small benthic invertebrates and drifting zooplankton, including suspended crustaceans. Its mouth is large relative to its overall size, and appetite follows accordingly, so prey items need not be tiny to be accepted.

In the aquarium it takes most foods offered, with frozen mysis shrimp and enriched brine shrimp among the most reliable staples. Artemia and krill round out a varied rotation. Feed once or twice daily, ideally in the evening when the fish is naturally most active, which also reduces competition from faster daytime feeders and helps a new specimen begin eating.

Frozen Mysis Shrimp Enriched Brine Shrimp Artemia Krill Small Marine Carnivore Preparations
Black Striped Cardinalfish are calm and non-aggressive, relying on concealment rather than speed or confrontation. During daylight hours they hover almost motionless near cover, then grow noticeably more active at dusk and through the night. They may be kept singly, in pairs, or in small loose groups, though group members can squabble among themselves when space or food is in short supply, so provide multiple shelters and feed enough to go around.

Choose tankmates that are peaceful and measured in their feeding. Aggressive or territorial fish, and boisterous fast feeders that strip food from the water column, will stress this species and can leave it underfed. Toward corals it is well behaved, with no evidence of coral damage, but it is reef safe with caution because small crustaceans are fair game. Small ornamental shrimp, and occasionally very small fish, may be eaten, which makes it a questionable choice for invertebrate-focused displays.

FAQ

Frequently Asked Questions

About the Black Striped Cardinalfish

  • Is the Black Striped Cardinalfish safe with shrimp and small crabs?
    It does not harm corals, but it can prey on small crustaceans such as small shrimp and may occasionally take very small fish. Use caution in tanks stocked with delicate invertebrates.
  • How large an aquarium does this cardinalfish need?
    Recommendations vary, from about 30 gallons at the low end to roughly 132 gallons at the high end. Lean toward the larger volume if you plan to keep more than one.
  • When is the best time to feed this species?
    Feed once or twice daily, preferably in the evening, since the fish becomes most active during low-light and nighttime hours.