Saddle blenny

Geographical Origin and Habitat: This species is distributed in the tropical Western Pacific, with records in Palau, Papua New Guinea (including the Trobriand and Umboi Islands), and the Solomon Islands. It inhabits shallow, sheltered coral reefs at depths of 1 to 6 meters, typically in areas dense with stony corals.

Taxonomy and Morphology: Belongs to the family Blenniidae, genus Ecsenius. It is a small marine blenny, reaching a maximum total length of about 4.1 cm in adult males. It features an elongated cylindrical body, a rounded head with a downward-facing mouth equipped with flexible, comb-like teeth.

Social Behavior: A solitary species that occupies small territories on the coral reef. It is active during the day, spending its time perched on rocks or corals to graze on algae or watch its surroundings. It can show territorial behavior toward other blennies or similarly shaped fish.

Coloration and Sexual Dimorphism: Displays a body with a base color ranging from light brown to olive, marked by a distinct dark saddle-like patch on the dorsal area, which gives it the specific name sellifer. Sexual dimorphism is weak; males may be slightly larger and show more saturated breeding colors.

Aquarium Setup: Requires a well-established aquarium of at least 60-80 liters. It is crucial to provide a large amount of live rock with plenty of holes and small crevices where the fish can hide and rest. The rockwork should have flat surfaces exposed to light to promote benthic algae growth.

Diet and Feeding: Primarily herbivorous. In nature, it feeds on benthic microalgae. In captivity, feed high-quality vegetable-based foods containing spirulina, sheets of nori algae, and frozen herbivore preparations. Occasionally, it will accept small protein foods like brine shrimp.

Water Quality: Standard stable marine conditions are required: temperature 23 to 26 °C, pH 8.1-8.4, specific gravity 1.020-1.025. Efficient filtration and moderate water movement are recommended to maintain a healthy environment and encourage the growth of natural algae biofilms.

Compatibility and Cohabitation: Generally reef-safe, but in smaller tanks, it may nip at stony coral polyps (SPS/LPS) if alternative food is scarce. Cohabits peacefully with calm reef fish. Avoid housing with other Ecsenius blennies or aggressive bottom-dwelling species.

Aquarium Breeding: Not common in captivity. It is an oviparous species; adhesive eggs are deposited inside small crevices and guarded by the male. Hatching occurs within days, and the pelagic larvae require microscopic live foods (rotifers) to survive the initial growth stage.

Risks and Diseases: A hardy and adaptable fish. The main risk is malnutrition if introduced into sterile tanks lacking natural algae to graze on. As with other blennies, the aquarium must be securely covered to prevent the fish from jumping out of the tank.