Yelloweye Combtooth Blenny

Geographical Origin and Habitat: Mainly restricted to the tropical waters of the Central and Western Pacific Ocean, ranging from the Mariana, Marshall, and Caroline Islands south to Samoa and Fiji. It inhabits shallow, coral-rich outer reefs, surge zones, and reef crests exposed to moderate currents at depths of 1 to 15 meters.

Taxonomy and Morphology: A member of the Blenniidae family in the genus Ecsenius. Commonly known as the Yelloweye Combtooth Blenny. It is a diminutive fish, reaching a maximum adult length of only 4 to 5 centimeters. The scale-less body is elongated, featuring specialized comb-like teeth used for scraping algae off rocky substrates.

Social Behavior: A peaceful and highly characterful fish. It spends its active hours perching on rockwork or coral branches, watching the surrounding area with curious eye movements. When threatened, it makes a rapid backward dart into a small hole or crevice in the live rock, leaving only its head protruding to watch for danger.

Coloration and Sexual Dimorphism: The body color is semi-translucent or pale beige, marked with thin, horizontal orange, red, or light brown stripes running along the sides. The most distinguishing feature is the large eyes, which are framed by a highly prominent, bright lemon-yellow ring. There is no visible sexual dimorphism.

Aquarium Setup: Ideal for mature nano-reefs of at least 80 liters (20 gallons). The tank must be designed with plenty of mature live rock containing small holes and crevices (branched coral rocks are perfect) where the fish can establish territories. A secure mesh screen or lid is mandatory to prevent the fish from jumping out of the tank.

Diet and Feeding: Strictly herbivorous. In the aquarium, they spend their time grazing on rocks, consuming diatoms and filamentous microalgae. Supplement their diet with high-quality spirulina flakes, dried nori seaweed, and herbivore pellets. They may occasionally consume frozen brine shrimp, but a lack of vegetable fiber will cause digestive issues.

Water Quality: Keep water conditions stable: temperature 23-27°C (73-81°F), pH 8.1-8.4, specific gravity 1.020-1.025, and GH 15-25. Regular water changes are essential to prevent nitrate accumulation. They are sensitive to poor water quality, ammonia spikes, and copper-based medications.

Compatibility and Cohabitation: 100% reef-safe. They do not harm corals, though they may occasionally perch on coral branches, causing brief polyp retraction. Peaceful towards other community fish; do not house them with large, aggressive predators or fast-swimming territorial fish that might prevent them from feeding.

Aquarium Breeding: Captive breeding is very rare and challenging. They spawn adhesive eggs inside small rock crevices, which are guarded and fanned by the male until they hatch. Raising the tiny pelagic larvae is difficult due to their requirement for specialized live rotifers and microalgae.

Risks and Diseases: The primary risk is starvation if introduced to a brand-new, sterile aquarium lacking natural microalgae growth on the rocks. Additionally, territorial conflicts can occur with other blennies of similar size or species (such as other Ecsenius) if kept in small aquariums with insufficient hiding spots.