Forktail Blenny (Meiacanthus atrodorsalis)

The Forktail Blenny, also widely known as the Yellowtail Fangblenny or Eyelash Harptail Blenny, is a favorite among reef keepers for its sleek silhouette, active personality, and unique defensive capabilities. Unlike many other blennies that spend their time perching on rocks, the Forktail is a "Fang Blenny," meaning it has a well-developed swim bladder that allows it to hover and glide gracefully in the mid-water column.

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Key Information

• Common Names: Forktail Blenny, Yellowtail Fangblenny, Eyelash Harptail Blenny

• Scientific Name: Meiacanthus atrodorsalis

• Origin: Western Pacific (Indonesia to Samoa, north to Japan)

• Max Size: 11 cm (approx. 4.3 inches)

• Lifespan: 5–8 years

• Temperament: Peaceful; relatively bold for its size

• Diet: Omnivore – Primarily feeds on zooplankton and small benthic invertebrates

• Care Level: Easy

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Appearance & Identification

The Forktail Blenny is prized for its elegant color gradient and graphic markings:

• Coloration: Features a soft, powder-blue to silver face that transitions into a vibrant yellow toward the rear of the body and tail.

• "Eyelash" Mark: A signature black diagonal line runs through the eye, giving the fish its "eyelash" moniker.

• Forked Tail: Adults develop a deeply forked (lyretail) caudal fin with long, delicate filaments on the tips.

• Black Fin Stripe: A distinct black stripe typically runs along the base or top of the dorsal fin.

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Behavior & Tank Compatibility

The Forktail Blenny is an "inoffensive" but well-armed resident. It possesses two venomous canine teeth in its lower jaw used strictly for self-defense.

• Dither Fish: Because it feels secure due to its venomous fangs, it swims openly in the water column. This "confidence" often encourages shy tank mates to come out of hiding.

• Reef Safe: 100% Reef Safe with corals. However, use caution with very small shrimp or tiny feather dusters, as larger adults may occasionally snack on them.

• Social Structure: Best kept singly or as a mated pair. Males can be territorial toward other Meiacanthus species or fish with similar shapes.

• Venom Note: While the bite is not typically dangerous to humans, it can be painful (similar to a bee sting). Use caution when performing maintenance near their favorite hiding spots.

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Ideal Tank Setup

• Tank Size: A minimum of 115L (30 Gallons) is recommended to provide sufficient swimming room.

• Rockwork: Provide plenty of live rock with small caves and crevices. Despite being an open swimmer, they love to dart into a "home base" for sleeping or when threatened.

• Lid: A tight-fitting lid is mandatory. Like all blennies, they are notorious and expert jumpers.

• Feeding: They have high metabolisms and do best with 2–3 small feedings per day. Offer a variety of frozen mysis, enriched brine shrimp, and high-quality flakes/pellets.