Bicolor fangblenny

Geographical Origin and Habitat: Plagiotremus laudandus is widely distributed in the tropical Western Pacific Ocean, ranging from the Philippines and Indonesia to Samoa, north to southern Japan, and south to the Great Barrier Reef and New Caledonia. It is typically found in clear lagoon reefs and seaward reef slopes at depths between 2 and 30 meters, where it swims actively in the water column looking for hosts.

Taxonomy and Morphology: Belonging to the family Blenniidae, tribe Nemophini, this species is characterized by an elongated, eel-like body that allows for rapid, snake-like swimming movements. It possesses a subterminal mouth equipped with a pair of enormous, curved canine teeth (fangs) in the lower jaw. These fangs are used for defense and for biting pieces off other fish. Adults grow to about 7-8 cm.

Social Behavior: This blenny is famous for its aggressive Batesian mimicry. It mimics the color pattern and swimming style of the venomous blenny Meiacanthus atrodorsalis. Trusting fish mistake Plagiotremus laudandus for the harmless model, allowing it to get close enough to launch a sudden attack, biting off chunks of scales, skin, or protective mucus. It is highly solitary and territorial.

Coloration and Sexual Dimorphism: The body coloration is light blue-grey on the anterior half, fading into a bright yellow on the posterior half and caudal fin, perfectly copying its mimicry target. A distinct black line runs through the eye. There is no significant sexual dimorphism, although males may become slightly more territorial and exhibit color changes during spawning periods.

Aquarium Setup: Requires an aquarium of at least 200 liters with plenty of live rock containing small holes or empty tube worm shells. These holes are essential as the fish retreats into them tail-first, leaving only its head exposed to monitor the tank. A secure, tight-fitting lid is absolutely mandatory, as this slender species is an exceptional jumper.

Diet and Feeding: In the wild, its diet consists of fish scales, mucus, and epidermal tissues. In captivity, training them to accept dead food is highly challenging. They must be fed multiple times a day (3-4 times) with small, meaty items like mysis shrimp, enriched brine shrimp, copepods, and high-quality paste foods. Established live rock with micro-fauna helps support them.

Water Quality: High water quality with strong filtration and oxygenation is necessary. Keep water parameters stable: temperature 24-28 °C, pH 8.1-8.4, and salinity 1.021-1.025. It has low tolerance for ammonia and nitrite, and high nitrate levels can cause significant chronic stress, weakening the fish's immune system.

Compatibility and Cohabitation: Highly problematic for standard community tanks. It will constantly harass large, slow-moving fish (such as surgeonfish, angels, and rabbitfish) to feed on their slime coat, leading to open wounds and severe stress. It should not be kept with Meiacanthus atrodorsalis to avoid territorial fights. Best suited for species-specific tanks or with fast-swimming fish.

Aquarium Breeding: Breeding in home aquariums is extremely rare. It is an oviparous species, depositing adhesive eggs inside narrow caves or tubes. The male guards the nest until the larvae hatch. Raising the pelagic larvae is difficult due to their microscopic size and the need for specific live cultures like rotifers.

Risks and Diseases: The primary risk is starvation due to dietary specialization and refusal of prepared foods. Their bite can cause physical damage to tankmates, which can lead to secondary bacterial infections. They are moderately susceptible to marine ich if stressed by poor water quality or aggressive tankmates.