Chestnut Blenny (Cirripectes castaneus)

The Chestnut Blenny is a small and uniquely patterned blenny species, distinguished by its reddish-brown coloration. Known for its peaceful nature and algae-grazing behavior, this blenny is a great addition to small and medium-sized reef or community aquariums. A fascinating behavior of the Chestnut Blenny is seen in the males, which turn a striking yellow color during mating season, adding a vibrant display to the aquarium.

Care Information

• Maximum Size: Up to 4 inches.
• Tank Size: 30 gallons minimum, with plenty of live rock for grazing and hiding.
• Diet: Herbivorous; primarily feeds on algae, but will also accept high-quality marine algae flakes, pellets, and occasional meaty foods like mysis shrimp.
• Water Temp: 72-78°F.
• Salinity: 1.020-1.025.
• Aggression: Peaceful; does well in community tanks but may become territorial toward other blennies or similar fish in smaller tanks.
• Skill Level: Beginner to Intermediate; hardy and relatively easy to care for, making it a good choice for new hobbyists.
• Reef Compatibility: Reef-safe; does not harm corals or invertebrates and is beneficial for controlling algae growth.

Color Variation by Locality

• Western Pacific: Exhibits a reddish-brown body with mottled patterns. In some regions, the coloration may be darker with more pronounced patterns.
• Indo-Pacific: Fish in this area may show lighter shades of brown with subtle differences in patterning depending on habitat​.

Unique Mating Behavior

• Color Change: During the mating season, male Chestnut Blennies display a striking transformation, changing to a vibrant yellow color to attract females​.

Typical Habitat

• Distribution: Found throughout the Western Pacific, including areas like Indonesia, the Philippines, and the Great Barrier Reef. The species inhabits shallow coral reefs and rocky outcroppings where it can graze on algae growing on the substrate​