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The Bicolor Blenny (Ecsenius bicolor) is a small, charismatic marine fish belonging to the family Blenniidae. It is well-known for its striking coloration, typically featuring a distinct two-toned body, which gives it its common name. These blennies are benthic, spending most of their time perched on rocks or corals, often darting into small crevices for shelter. They are popular in the aquarium trade due to their vibrant appearance, relatively small size, and interesting personalities.
Physical Characteristics
- Body shape
- elongated
- Coloration
- The anterior half of the body is typically dark brown, black, or deep blue, transitioning abruptly to a bright orange, red, or yellow posterior half, including the caudal fin. Color intensity can vary based on mood, health, and geographic location. Some individuals may exhibit a more uniform dark coloration or a less distinct bicolor pattern.
- Scale type
- none
- Mouth position
- inferior
- Distinctive features
- Prominent cirri (small fleshy filaments) above the eyes, though less elaborate than some other blenny species., A single, continuous dorsal fin., Small, comb-like teeth (hence 'combtooth blenny')., Often perches on its pelvic fins.
- Dorsal fin
- Single, long dorsal fin with 11-12 spines and 14-16 soft rays. The spiny and soft-rayed portions are continuous.
- Tail fin
- Rounded caudal fin.
- Pectoral fin
- Large, fan-like pectoral fins used for perching and maneuvering.
- Distinctive fins
- Pelvic fins are jugular (located anterior to the pectoral fins) and modified into thick, fleshy rays used for support and perching.
Identification Tips
Coloration
The most defining feature is the distinct two-toned body, typically dark anterior and bright orange/yellow posterior. However, be aware of color variations.
Body Shape
Elongated, slender body typical of blennies, with a relatively large head.
Behavior
Often seen perching on rocks or corals, using their pelvic fins for support, and darting into holes when startled.
Size
Small fish, rarely exceeding 11 cm (4.3 inches) in total length.
Habitat
- Water type
- saltwater
- Depth
- Typically found in shallow reef environments, from 1 to 30 meters (3 to 100 feet).
- Environment
- Coral reefs, rocky areas, and rubble zones. They prefer areas with abundant crevices, holes, and empty mollusk shells for shelter. They are often seen perched on live rock or coral branches.
- Geographic range
- Indo-Pacific region, ranging from the Red Sea and East Africa eastward to Samoa, north to the Ryukyu Islands, and south to the Great Barrier Reef and New Caledonia.
Aquarium Information
- Care level: beginner
- Temperament: peaceful
- Diet: omnivore
- Minimum tank size: 20 gallons
- Temperature: 72-78°F (22-26°C)
- pH level: 8.1-8.4
- Hardness: 8-12 dKH
- Compatibility: Generally peaceful with other fish, but can be territorial towards conspecifics or similar-looking blennies in smaller tanks. Best kept singly unless in a very large tank with ample hiding spots.
- Special requirements: Requires plenty of live rock with crevices and holes for hiding and perching. A well-established tank with mature algae growth is beneficial as they graze on microalgae. A tight-fitting lid is essential as they are known jumpers.
Wild Information
- Conservation status: least concern
- Seasonality: No specific seasonality for reproduction or migration is widely documented; they are present year-round in their native habitats.
- Market price: Varies, typically $15-$30 USD for a single specimen.
- Commercial importance: medium
- Taste: Not typically consumed due to small size.
- Texture: Not typically consumed due to small size.
- Nutritional value: Not typically consumed due to small size.
Key Facts
Color Changebehavior
Bicolor Blennies can sometimes change their coloration significantly, even appearing entirely dark or light, depending on their mood, environment, or stress levels.
Mimicryinteresting
Some blennies, though not E. bicolor specifically, are known for mimicry, imitating venomous blennies to deter predators. E. bicolor itself is not a mimic.
Algae Grazerbehavior
They play a role in reef ecosystems by grazing on microalgae, helping to keep coral surfaces clean.
Territorial but Peacefulbehavior
While generally peaceful towards other fish species, Bicolor Blennies can be quite territorial towards other blennies, especially conspecifics, and will defend their chosen crevice or perch.
Safety Information
Safe- Safety level: safe
- Venomous: No
- Edibility: not recommended
- Handling notes: No specific handling precautions are required beyond standard fish handling practices. They are not venomous and do not possess sharp spines that pose a significant threat. They may nip if handled, but their teeth are very small.
Similar Species
Tailspot Blenny
Ecsenius stigmatura
Lacks the distinct bicolor pattern, typically has a more uniform body coloration with a prominent black spot on the caudal fin base.
Midas Blenny
Ecsenius midas
Generally a uniform golden-yellow to orange color, often with a more elongated body and a tendency to swim in the water column more frequently than E. bicolor.
Red Sea Mimic Blenny
Ecsenius gravieri
While also having a bicolor pattern, E. gravieri typically has a more reddish-brown anterior and a lighter posterior, and its range is restricted to the Red Sea and Gulf of Aden. The color transition can be less abrupt than in E. bicolor.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Blenniiformes
- Family
- Blenniidae
- Genus
- Ecsenius
- Species
- Ecsenius bicolor
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