Red Stoplight Cardinalfish Also known as Stoplight Cardinalfish, Iridescent Cardinalfish The Red Stoplight Cardinalfish is a beautiful and unique species displaying iridescent red to orange coloration with a distinctive bright spot behind the eye that resembles a stoplight. This peaceful and hardy cardinalfish is less commonly seen than other cardinals but makes an excellent addition to peaceful reef aquariums. Key Features Scientific Name: Apogonichthys hyalinus Common Names: Stoplight Cardinalfish, Susan’s Cardinalfish Adult Size: Up to 2.5 inches Lifespan: 3-5 years with proper care Temperament: Very peaceful and shy; does well in small groups Reef Compatibility: Completely reef safe; will not harm corals or invertebrates Minimum Tank Size: 30 gallons minimum Experience Level: Beginner to moderate; hardy once acclimated Habitat & Tank Requirements Tank Environment: Provide plenty of caves, overhangs, and sheltered areas among live rock. This shy species needs secure hiding spots and low to moderate lighting. Prefers calm water flow. Water Parameters: Temperature: 72-78°F (22-26°C) Salinity: 1.020-1.025 pH: 8.1-8.4 Adaptable to typical reef conditions Equipment Recommendations: Standard filtration system Protein skimmer Gentle water circulation These maintain stable conditions for this peaceful species. Diet & Feeding Red Stoplight Cardinalfish are carnivores requiring meaty foods. Recommended foods include: Staples: High-quality marine pellets, carnivore pellets (small size) Frozen Foods: Mysis shrimp, brine shrimp, cyclops, copepods, finely minced seafood Live Foods: Live brine shrimp (helpful during initial acclimation) Feeding Frequency: Once or twice daily Special Note: Small mouth requires appropriately sized food particles; may take time to accept prepared foods Social Structure & Group Dynamics Can Be Kept in Small Groups: Naturally forms pairs or small aggregations Pairing Behavior: Often pairs off; males are mouth-brooders Very Peaceful: Non-aggressive toward conspecifics and all other species Introduce Simultaneously: Pairs or groups do best when added together Notes & Considerations Distinctive iridescent red-orange coloration with bright “stoplight” spot behind eye. Less commonly available than Banggai or Pajama Cardinals but equally hardy. Primarily nocturnal; most active during evening and nighttime hours. Will become bolder and more visible during the day once fully acclimated. Small size and peaceful nature make it ideal for nano reef aquariums. May be shy initially and hide frequently until comfortable. Should not be kept with aggressive or boisterous tankmates. Slow-moving; ensure adequate food reaches them in tanks with competitive feeders. Males may mouth-brood eggs in home aquariums under proper conditions. Prefers dimmer lighting or tanks with shaded areas and caves. Excellent choice for peaceful, low-aggression community reef tanks. Why Choose a Quarantined Red Stoplight Cardinalfish? Purchasing a quarantined specimen from us means you’re starting with a healthier, better-acclimated fish. All fish are observed, treated as needed, and conditioned to accept prepared foods before sale, giving you a stronger chance of long-term success with this beautiful and peaceful species.
