QUICK STATS

Care Level: Easy to Moderate
Diet: Omnivore / Herbivore-Leaning
Temperament: Peaceful to Mildly Territorial
Reef-Safe: Yes, With Caution
Venomous/Toxic: No
Approximate Purchase Size: 1.5-3"
Approximate Max Size: Around 4"
Recommended Tank Size: 30 Gallons or Larger

BICOLOR BLENNY

The Bicolor Blenny (Ecsenius bicolor) is a popular saltwater aquarium fish known for its two-tone coloration, curious personality, and entertaining perching behavior. Most individuals have a darker front half with a bright orange to yellow rear half, giving them a bold contrast that stands out nicely against live rock.

Bicolor Blennies are usually hardy, active, and full of personality. They spend much of their day hopping across rockwork, perching in small holes, and inspecting the aquarium like a tiny judgmental landlord. They are a great choice for established reef aquariums with plenty of live rock, hiding spots, and natural grazing surfaces.

This species is generally considered reef-safe, but it should still be kept with some caution. Most Bicolor Blennies leave corals and invertebrates alone, though some individuals may occasionally nip at fleshy coral tissue, clam mantles, or other sessile invertebrates. So yes, mostly charming, but still technically a fish with free will. Annoying little loophole.

Note: Image is a representation of what to expect. The fish you receive may vary slightly in size, color, pattern, and overall appearance.

AQUARIUM REQUIREMENTS

AQUARIUM SIZE

A minimum tank size of 30 gallons or larger is recommended for a Bicolor Blenny. While they stay relatively small, they need enough rockwork, grazing surface, and territory to feel secure.

Larger aquariums provide more stability, more algae and biofilm for grazing, and more room to reduce territorial behavior toward similar-shaped fish.

HABITAT RECOMMENDATIONS

Bicolor Blennies do best in established aquariums with plenty of live rock, hiding places, and stable water quality.

Aquascaping: Provide live rock with caves, holes, ledges, and crevices. Bicolor Blennies often choose a favorite hole or perch and return to it throughout the day like they are clocking into a tiny reef office.

Substrate: Sand or fine aragonite works well and helps create a natural reef-style environment.

Rockwork: Live rock is strongly recommended. It gives the blenny places to hide, perch, and graze throughout the day.

Tank Maturity: A mature aquarium is preferred, especially one with natural algae and biofilm growth. A spotless new tank may not provide enough natural grazing.

Tank Cover: A tight-fitting lid is recommended. Blennies are known jumpers, because apparently living underwater was not enough of a commitment.

WATER PARAMETERS

Bicolor Blennies are considered hardy, but they still need clean, stable marine conditions. “Hardy” does not mean “throw it into chaos and let hope do the filtration.”

Temperature: 75-80°F
pH Level: 8.1-8.4
Salinity: 1.020-1.026 specific gravity
Ammonia, Nitrite, and Nitrate: Ammonia and nitrite should remain undetectable. Nitrate should be kept as low as reasonably possible, ideally below 20 ppm.
Water Flow: Low to moderate flow is ideal. Provide enough water movement to keep the aquarium oxygenated and move waste toward filtration, while still giving the blenny calmer areas to perch and graze.

DIET

Bicolor Blennies are omnivores with a strong preference for algae-based foods and natural grazing. They spend much of their time picking at rockwork, glass, and other surfaces for algae, film, and tiny food particles.

PRIMARY DIET

Frozen Food: Offer mysis shrimp, enriched brine shrimp, marine blends, and other small frozen foods. We at Summit City Coral prefer frozen foods such as LRS Herbivore Frenzy and PE Mysis.

Prepared Omnivore Foods: High-quality marine pellets, flakes, and omnivore blends can help provide a balanced diet. Smaller food sizes are best, especially for smaller individuals.

Algae-Based Foods: Spirulina flakes, herbivore pellets, algae wafers, nori, and herbivore blends should be included regularly.

Natural Grazing: Established live rock with film algae and biofilm can help support natural feeding behavior. This does not mean the blenny should be expected to solve an algae problem alone, because fish are not unpaid maintenance staff, no matter how suspiciously useful they look.

FEEDING FREQUENCY

Feed small amounts 1-2 times per day. In very clean aquariums, regular supplemental feeding is especially important so the blenny does not run out of natural grazing material.

COMPATIBILITY

Bicolor Blennies are generally peaceful and work well in community reef aquariums. They may become territorial toward other blennies, gobies, or similarly shaped fish, especially in smaller aquariums.

COMMON TANK MATES

Fish: Clownfish, cardinalfish, wrasses, firefish, tangs, dwarf angelfish, chromis, and other peaceful to semi-peaceful community fish.

Avoid: Other blennies or similarly shaped bottom-perching fish in smaller aquariums unless there is enough space and rockwork to reduce territorial conflict. Also avoid large predatory fish that may eat them.

Invertebrates: Bicolor Blennies are usually safe with most cleaner shrimp, hermit crabs, snails, urchins, and other common reef invertebrates.

Coral: Bicolor Blennies are generally considered reef-safe with caution. Most individuals ignore coral, but occasional nipping at fleshy corals, clam mantles, or sessile invertebrates is possible.

BEHAVIORAL NOTES

Temperament: Peaceful overall, though they may defend a favorite hole, perch, or section of rockwork.

Personality: Very curious and active. Bicolor Blennies often perch in plain view and watch the room like they are silently reviewing everyone’s choices.

Perching Behavior: They frequently hop from rock to rock rather than swimming constantly in open water.

Algae Grazing: They may help graze film algae and soft algae growth, but they should not be treated as a complete algae-control solution.

Reef Compatibility: Usually excellent for reef tanks, though individual behavior can vary around clams and fleshy corals.

Territoriality: May show aggression toward other blennies, gobies, or similar-shaped fish, especially in smaller systems.

Jumping: A tight-fitting lid is strongly recommended. Blennies are athletic in the worst possible way.

ACCLIMATION PROCESS

This acclimation method helps reduce stress by gradually introducing the fish to your aquarium’s temperature and water chemistry.

1. TURN OFF THE LIGHTS & ATO

Turn off aquarium lights to reduce stress. If you have an Auto Top Off system, switch it off before starting acclimation.

2. FLOAT THE BAG

Float the sealed bag in the aquarium for 15-20 minutes to allow the temperature in the bag to equalize with the tank.

3. OPEN BAG, ADD FISH TO CONTAINER

Carefully open the bag and transfer the fish and shipping water into a clean bucket or container.

4. ACCLIMATE USING TANK WATER

Add 1/4 cup of tank water to the container every 5 minutes for 40 minutes.

5. TRANSFER FISH TO AQUARIUM

Once acclimation is complete, gently transfer the fish into the aquarium using a net or specimen container. Discard the shipping water. Do not pour shipping water into your aquarium.

6. REFILL THE AQUARIUM WITH SALTWATER

You may need to replace the saltwater removed during acclimation with fresh mixed saltwater.