Yellowtail Blenny (Ecsenius flavipes)

Also Known As: Yellowtail Black Blenny, Flametail Blenny

Compatibility and Behavior
The Yellowtail Blenny (Ecsenius flavipes) works a bold, blocky color scheme: a velvety black body set against a vividly yellow tail and rear dorsal and anal fins, a contrast that grabs your eye the moment it goes in the tank. It's easy to mix up with the Bicolor Blenny, so here's how to tell them apart: the Yellowtail has a more rounded, streamlined head, lacks the antenna-like cirri between the eyes, and shows a cleaner, rounded tail that tends to be solid yellow rather than the more angular, orange-toned tail of a Bicolor. It's generally peaceful and reef safe, spending most of its day perched on ledges and rock faces picking microalgae and biofilm off the live rock rather than bothering corals or inverts. Like the other perching blennies, it can get territorial toward other blennies, small gobies, or dartfish that share its body shape or feeding niche, especially in smaller tanks, so it's best kept as the only blenny unless the system is large and heavily rock-scaped. Otherwise it coexists well with clownfish, cardinalfish, small wrasses, firefish, and other calm reef fish, adding both grazing utility and plenty of personality. It's a capable jumper when startled or competing for territory, so a tight-fitting lid or mesh screen is strongly recommended.

Aquarium Requirements
As with all the grazing blennies, an algae-rich tank is the real requirement. It does best in an established system around 20 to 30 gallons or larger that's been running several months with healthy microalgae and biofilm on the rock, since it leans on that natural growth to feed, and in a very clean tank it should get regular algae-based prepared foods to prevent slow starvation. Arrange plenty of live rock into caves, crevices, and platforms for perching and hiding. Moderate flow that keeps rock surfaces oxygenated and moves detritus into filtration suits its grazing lifestyle, and stable reef-quality water supports both the fish and the food it depends on. Supplement its grazing with spirulina-rich flakes and pellets, nori or marine algae sheets, and small meaty foods like mysis and brine a couple of times a day.

Specifications
Approximate Size: 1–2"
Diet: Omnivore leaning herbivore; primarily grazes film and filamentous algae and biofilm on live rock, supplemented with spirulina-rich flakes and pellets, nori or marine algae sheets, and small meaty foods such as mysis and brine shrimp
Origin: Western Indo-Pacific
Care Level: Moderate
Reef Safe: Yes
Temperament: Peaceful
Minimum Tank Size: 20 gallons
Special Considerations: Depends on natural algae and biofilm to graze, so it does best in an established tank with supplemental algae-based feeding to prevent starvation in clean systems; can be territorial toward other blennies, small gobies, or dartfish with a similar body shape, so best kept as the only blenny unless the tank is large; a capable jumper, so a tight-fitting lid is recommended