Iridescent Cardinalfish

The Iridescent Cardinalfish is a small and fascinating species known for its shimmering, iridescent body that displays shifting hues of blue, green, and silver depending on the angle of light. Native to the Western Pacific, this species has a remarkable ecological relationship with long-spined sea urchins, among whose protective spines it shelters during the day. This symbiotic association provides the tiny cardinalfish with protection from predators while the urchin host appears unaffected by its presence.

In the home aquarium, the Iridescent Cardinalfish requires slightly more care than many other cardinalfish, earning it an intermediate care rating. The key to success with this species is providing appropriate shelter, ideally in the form of long-spined sea urchins such as Diadema species. Without this natural host, substitute shelter can be provided through dense branching corals or intricate rockwork with many small crevices. This species can be shy initially and may require live foods such as enriched brine shrimp or copepods before transitioning to frozen preparations.

The Iridescent Cardinalfish is fully reef-safe and its diminutive size means it poses no threat to any corals or invertebrates. Due to its small size and somewhat delicate nature, it should only be housed with equally peaceful and small tankmates. This species is best suited for dedicated nano reefs or species-specific setups where its unique iridescent beauty and fascinating urchin-associated behavior can be fully appreciated.