Red Stop Light Cardinalfish

The Red Stop Light Cardinalfish is a diminutive and fascinating species that earns its common name from a vivid red spot on its otherwise largely transparent body. This small, glass-like fish appears almost ethereal in the aquarium, with its near-invisible body revealing internal structures while the bright red marking serves as its signature feature, resembling a tiny stoplight glowing in the water.

This species is found in the Western Pacific, where it inhabits sheltered lagoons and inner reef areas. Its tiny size and transparent body provide natural camouflage among coral branches and sea grass beds. In the wild, it forms small schools that move as a coordinated unit, the red spots of multiple individuals creating an intriguing visual pattern as they drift through their habitat.

The Red Stop Light Cardinalfish is an excellent candidate for nano reef aquariums, where its diminutive size can be fully appreciated in an appropriately scaled environment. At just 2.5 inches maximum, it is one of the smallest cardinalfish species available in the hobby. Despite its delicate appearance, it adapts well to aquarium life and accepts prepared foods readily. Its peaceful nature and small bioload make it ideal for smaller reef setups.