Encyclopaedia

FishMarineEasy
©AI Generated·Proprietary

Forktail blenny

Meiacanthus atrodorsalis

The Forktail Blenny is an accomplished jumper from the Western Pacific. It needs a covered tank featuring live rock full of small crevices for shelter, while leaving sufficient open swimming space.

Taxonomy
Class:Actinopteri
Order:Perciformes
Family:Blenniidae
Genus:Meiacanthus
Species:Meiacanthus atrodorsalis

Share

Check out Forktail blenny on Atlarium

PracticeRecognition quizzesPhotos, names, origins, and puzzles to review Atlas species.Open quizzes
Water Temperature

23 - 28 °C

pH Value

8 - 8.5

Water type

Marine

Tank level

All levels

Adult size

11 cm

Minimum tank volume

>= 115 L

Minimum group

>= 1

KH

8 - 12 dKH

Species description

Geographical Origin and Habitat: The Forktail blenny is widely distributed across the Western Pacific Ocean, ranging from Bali in Indonesia to the Line Islands, north to southern Japan, and south to the Great Barrier Reef in Australia. It inhabits clear lagoons and seaward reefs, often seen hovering in mid-water near branching corals at depths between 1 and 30 meters.
Taxonomy and Morphology: Belonging to the family Blenniidae, Meiacanthus atrodorsalis is characterized by its slender, elongated body and a deeply forked caudal fin with long filaments. A unique biological feature is the presence of toxic canine teeth in the lower jaw, which it uses defensively to bite the inside of a predator's mouth if swallowed.
Social Behavior: Unlike most blennies that dwell on the substrate, this species is an active swimmer that spends a significant amount of time in the water column. It is generally peaceful, bold, and curious, coexisting well with most reef community fish. However, territorial conflicts may occur between males if housed in small aquariums.
Coloration and Sexual Dimorphism: The body coloration is highly striking, featuring a bright blue-gray anterior that blends into a vivid yellow-green posterior and tail. A prominent dark diagonal stripe runs through the eye. Males are typically larger than females and develop more pronounced, elongated extensions on their tail fin.

Care, breeding and tankmates

Aquarium Setup: An aquarium of at least 100 liters with a secure, tight-fitting lid is essential, as this species is an accomplished jumper. The tank layout should include plenty of live rock with small holes, crevices, and caves where the blenny can shelter at night or when startled, while leaving open space for swimming.
Diet and Feeding: Primarily a carnivore that feeds on zooplankton in the wild. In the aquarium, it easily acclimates to a wide range of foods, including frozen mysis shrimp, brine shrimp, and high-quality pellet or flake foods. Feeding small portions multiple times a day is recommended to sustain its active lifestyle.
Water Quality: Requires clean, well-oxygenated water with moderate flow. Keep water temperature stable between 22°C and 26°C, pH between 8.1 and 8.4, and salinity (specific gravity) within the range of 1.020 to 1.025. Regular water changes and efficient filtration are necessary to maintain low nitrate levels.
Compatibility and Cohabitation: Excellent candidate for reef tanks (completely reef-safe). It will not harm corals, clams, or ornamental invertebrates. It coexists peacefully with most non-aggressive reef fish. Avoid housing with large predatory species that might try to eat it, as the venomous bite is defensive.
Aquarium Breeding: Breeding in captivity has been achieved. They are demersal spawners, depositing adhesive eggs inside small crevices, caves, or empty shells. The male guards and fans the egg clutch until they hatch. Raising the tiny larvae requires a steady supply of live rotifers and microalgae.
Risks and Diseases: Generally hardy and disease-resistant. However, like all scaleless fish, they are sensitive to external parasites like marine ich and can be highly sensitive to copper-based medications. Handle with care, as their defensive bite can cause local pain and swelling in humans.

Geographic Origin and Distribution

The Forktail blenny is widely distributed across the Western Pacific Ocean, ranging from Bali in Indonesia to the Line Islands, north to southern Japan, and south to the Great Barrier Reef in Australia. It inhabits clear lagoons and seaward reefs, often seen hovering in mid-water near branching corals at depths between 1 and 30 meters.

Origin

Tropical oceans and reefsAfrica and MadagascarSouth and Southeast AsiaEast AsiaAustralia, New Guinea, and Oceania

Fish profile

Temperament
Territorial
They are bold, active, and fascinating to watch as they constantly hover and swim in the open. While generally peaceful with other species, their venomous bite makes them completely fearless of larger fish. They will not hesitate to bite back if swallowed or attacked, often causing the predator to spit them out. They make a colorful, dynamic, and unique addition to a reef community.
Diet
Omnivore
This species is an omnivorous planktivore that feeds from the water column rather than grazing on rocks. They eagerly accept frozen foods like mysis shrimp, brine shrimp, and finely chopped seafood. High-quality marine flakes and micro-pellets are also usually taken with enthusiasm. A varied diet that includes some marine algae or spirulina will keep their colors bright and their immune systems strong.
Sex ratio
Flexible
It is highly recommended to keep only one individual per aquarium unless they are a proven, mated pair. Conspecifics or even similarly shaped blennies will engage in vicious, often fatal, combat. In very large tanks with abundant rockwork, multiple individuals might coexist, but the risk remains high. For the vast majority of home aquarists, keeping a single specimen is the safest choice.
Feeding frequency
Twice daily
They should be fed two to three times daily with small amounts they can quickly snatch from the water column. Since they have relatively small stomachs, frequent feeding mimics their natural continuous foraging behavior. They are quick and enthusiastic eaters that will aggressively compete for food. Automated feeders dispensing small sinking pellets are highly beneficial for them.
Bioload
Low
The Forktail Blenny produces a minimal bioload making them suitable for smaller marine aquariums. They do not significantly impact nitrate or phosphate levels if fed correctly. Standard marine filtration and regular, modest water changes are entirely sufficient to maintain excellent water parameters. They are quite hardy and resilient to minor fluctuations in water chemistry.
Flow
Strong
They appreciate moderate water flow that suspends food particles in the water column. Good flow encourages them to stay active and visible in the open water. Ensure there are calmer areas near the rockwork where they can retreat and rest when desired. Too much turbulent flow can exhaust them, as they constantly swim rather than perch.
Jump risk
Yes
They are known to be significant jumper risks, particularly when newly introduced to an aquarium. A tight-fitting lid, canopy, or mesh screen is absolutely mandatory to keep them safely inside. They often dart toward the surface when chased or spooked by sudden movements outside the tank. Do not underestimate their ability to find even the smallest escape route.
Reproduction
Oviparous
They are demersal spawners; the male courts the female and she lays adhesive eggs inside a tight crevice or empty shell. The male fiercely guards and aerates the egg clutch until they hatch. Captive breeding is very possible and happens regularly in well-established aquariums. Rearing the very small larvae, however, requires specialized cultures of rotifers and copepods.
Compatibility & tankmates
Community
They are generally peaceful and completely reef safe, paying no attention to corals or invertebrates. However, they possess venomous fangs which they use defensively, meaning aggressive tank mates will learn to leave them alone. They can be safely kept with a wide variety of peaceful community fish. Avoid keeping them with other fang blennies, as they will fight aggressively over territory.
Tank level
All levels
Unlike many blennies that perch on the substrate, they spend most of their time actively swimming in the mid-water regions. They will utilize the upper rockwork as a base to dart out and catch passing plankton. They require small caves or crevices in the live rock where they can sleep securely at night. They are very visible fish that utilize open swimming space extensively.

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Trophic level
3.5 ± 0.41 se
Resilience
High (less than 15 months)
Phylogenetic uniqueness (PD50)
0.5
Bayesian Length-Weight
a = 0.00575, b = 3.06
VulnerabilityLow vulnerability (10 / 100)

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

Related species

Recommendations grouped by close relatives, companion choices, and similar care.

Variants and close relatives

Same atlas type, nearby scientific identity, genus, or family.

Striped fangblenny

Striped fangblenny

Meiacanthus grammistes

View details->
Canary fangblenny

Canary fangblenny

Meiacanthus oualanensis

View details->
Harptail Blenny

Harptail Blenny

Meiacanthus mossambicus

View details->
Bundoon blenny

Bundoon blenny

Meiacanthus bundoon

View details->
One-stripe Fangblenny

One-stripe Fangblenny

Meiacanthus ditrema

View details->
Kamohara Blenny

Kamohara Blenny

Meiacanthus kamoharai

View details->
Gravier's Blenny

Gravier's Blenny

Ecsenius gravieri

View details->
Starry blenny

Starry blenny

Salarias ramosus

View details->
Two-spot bimaculatus blenny

Two-spot bimaculatus blenny

Ecsenius bimaculatus

View details->
Brown Coral Blenny

Brown Coral Blenny

Atrosalarias fuscus

View details->
Red-streaked blenny

Red-streaked blenny

Cirripectes stigmaticus

View details->
Beautiful Blenny

Beautiful Blenny

Ecsenius pulcher

View details->
Tailspot blenny

Tailspot blenny

Ecsenius stigmatura

View details->
Allen's blenny

Allen's blenny

Ecsenius alleni

View details->
Axelrod's blenny

Axelrod's blenny

Ecsenius axelrodi

View details->
Black combtooth blenny

Black combtooth blenny

Ecsenius namiyei

View details->

Recommended companions

Compatible cards from coherent ecosystems with matching parameters.

Grape caulerpa
Plant

Grape caulerpa

Caulerpa racemosa

View details->
Caulerpa prolifera
Plant

Caulerpa prolifera

Caulerpa prolifera

View details->
Caulerpa taxifolia
Plant

Caulerpa taxifolia

Caulerpa taxifolia

View details->
Chaetomorpha macroalgae
Plant

Chaetomorpha macroalgae

Chaetomorpha linum

View details->
Dead man fingers algae
Plant

Dead man fingers algae

Codium fragile

View details->
Halimeda macroalgae
Plant

Halimeda macroalgae

Halimeda opuntia

View details->
Peacock tail algae
Plant

Peacock tail algae

Padina pavonica

View details->
Red gracilaria
Plant

Red gracilaria

Gracilaria parvispora

View details->
Red grape algae
Plant

Red grape algae

Botryocladia uvaria

View details->
Sea lettuce
Plant

Sea lettuce

Ulva lactuca

View details->
Red Mangrove
Plant

Red Mangrove

Rhizophora mangle

View details->

Similar care

Cards with similar requirements, difficulty, habitat, and husbandry profile.

Wolf fangblenny

Wolf fangblenny

Petroscirtes lupus

View details->
Aurora Goby

Aurora Goby

Amblyeleotris aurora

View details->
Shorthead fangblenny

Shorthead fangblenny

Petroscirtes breviceps

View details->
Linear Blenny

Linear Blenny

Ecsenius lineatus

View details->
Ocular Blenny

Ocular Blenny

Ecsenius oculus

View details->
Orange-spotted Blenny

Orange-spotted Blenny

Blenniella chrysospilos

View details->
Canary damselfish

Canary damselfish

Chrysiptera galba

View details->
Barber Goby

Barber Goby

Elacatinus figaro

View details->
Five-lined Coral Goby

Five-lined Coral Goby

Gobiodon quinquestrigatus

View details->
Lawnmower Blenny

Lawnmower Blenny

Salarias fasciatus

View details->
Saddle blenny

Saddle blenny

Ecsenius sellifer

View details->
Yellowtail Clown Blenny

Yellowtail Clown Blenny

Ecsenius melarchus

View details->
Bicolor fangblenny

Bicolor fangblenny

Plagiotremus laudandus

View details->
Springer's Blenny

Springer's Blenny

Ecsenius springeri

View details->
Girdled goby

Girdled goby

Priolepis cincta

View details->
Ambon Chromis

Ambon Chromis

Chromis amboinensis

View details->
Last updated: 06/30/2026
Forktail blenny (Meiacanthus atrodorsalis) Care Guide & Tank Setup | Atlarium