Species description

Care, breeding and tankmates

Fish profile

Temperament

Active

The Fourline blenny is peaceful, highly observant, and full of personality. They spend hours perched on vantage points, observing the activities inside and outside the tank. Their comical expressions and darting movements make them a favorite among reef hobbyists.

Diet

Herbivore

This species is primarily an herbivore that continuously grazes on microalgae growing on the rockwork. Its diet should be supplemented with high-quality spirulina flakes, algae sheets, and occasional small meaty foods like mysis. Providing a mature tank with natural algae growth is essential for its long-term health.

Sex ratio

Solitary

They are generally best kept singly in small to moderately sized aquariums to prevent territorial disputes. If a male-female pair can be established, they will often coexist peacefully in the same tank. Mixing multiple males is highly discouraged as it will lead to severe aggression.

Feeding frequency

Continuous

Because they constantly graze throughout the day, supplemental feedings only need to occur once or twice daily. They have small stomachs designed for continuous feeding rather than large, infrequent meals. Keeping a clip of seaweed in the tank can help fulfill their grazing needs.

Bioload

The Fourline blenny is a small fish with a correspondingly low bioload. It contributes very little waste to the aquarium system, making it suitable for smaller setups. Standard filtration and regular maintenance are perfectly adequate to handle its needs.

Flow

Strong

They prefer moderate water flow, which helps promote the growth of the microalgae they feed upon. Good flow also mimics the reef crests and slopes where they naturally reside. They are adept at finding sheltered spots in the rockwork if the current becomes too intense.

Jump risk

Yes

Blennies in general are known to be capable jumpers, especially when startled or harassed. A tight-fitting lid or mesh top is strongly recommended to ensure they do not leap from the tank. Open-top aquariums carry a significant risk for this species.

Reproduction

Oviparous

They are demersal spawners, laying adhesive eggs in small crevices or empty shells within the rockwork. The male rigorously guards and fans the eggs until they hatch. While spawning in captivity occasionally occurs, raising the microscopic fry remains a significant challenge for most hobbyists.

Compatibility & tankmates

Reef safe

It is an incredibly peaceful fish that is highly considered reef safe, ignoring corals and larger invertebrates. It may occasionally nip at very small, sessile invertebrates, but damage is extremely rare. It gets along with almost any peaceful community fish, though it may quarrel with other closely related blennies.

Tank level

Middle/Bottom

They are classic bottom-dwellers that spend the vast majority of their time perched on live rock. They lack a swim bladder, meaning they 'hop' from rock to rock rather than swimming in the open water. They require plenty of caves and crevices to retreat into when feeling threatened.