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: 0.75-1.5"
Approximate Max Size: Around 1.5-2"
Recommended Tank Size: 20-30 Gallons or Larger

TWO SPOT BLENNY

The Two Spot Blenny (Ecsenius bimaculatus), also known as the Twinspot Bimaculatus Blenny or Two Spot Bimaculatus Blenny, is a tiny reef-safe blenny known for its small size, pale tan body, darker head markings, and two distinctive dark spots or bars along the middle of the body. It stays much smaller than many other blennies, making it a great option for nano reefs and smaller peaceful community aquariums.

Two Spot Blennies are active little perch fish that spend much of their day resting on rockwork, hopping between ledges, and grazing on film algae, biofilm, and tiny foods. They are not constant open-water swimmers. They are more like miniature reef gargoyles with snack priorities and suspiciously strong opinions for something barely larger than a frag plug.

This species is generally considered reef-safe, but like many small algae-grazing blennies, it should still be listed with caution. Most individuals leave corals alone, but occasional nipping at coral mucus, SPS polyps, fleshy tissue, or clam mantles can happen, especially if the fish is underfed or kept in a very clean aquarium with limited grazing. Reef-safe, yes. Free of blenny fine print, no. Naturally, the tiny fish also has terms and conditions.

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

AQUARIUM REQUIREMENTS

AQUARIUM SIZE

A minimum tank size of 20 gallons or larger is recommended for a Two Spot Blenny, though 30 gallons or larger is preferred for better stability, more grazing surfaces, and more room for tank mates.

While some sources list this species as suitable for very small aquariums, a slightly larger established system gives the fish more natural food availability and a safer long-term environment. Tiny fish still live inside chemistry, tragically.

HABITAT RECOMMENDATIONS

Two Spot Blennies do best in established aquariums with live rock, hiding places, and plenty of natural grazing surfaces.

Aquascaping: Provide live rock, caves, ledges, and small crevices. Two Spot Blennies enjoy perching on rockwork and darting into shelter when startled.

Substrate: Sand, fine aragonite, crushed coral, or bare-bottom systems can all work. This species does not rely heavily on the sandbed.

Rockwork: Live rock is strongly recommended. It provides shelter, territory, biological filtration, and natural grazing surfaces.

Tank Maturity: A mature aquarium is preferred, especially one with film algae and biofilm growth. Very new or overly sterile aquariums may not provide enough natural grazing.

Tank Cover: A tight-fitting lid is recommended. Small blennies can jump or disappear into overflow areas, because apparently being tiny also comes with terrible navigation software.

WATER PARAMETERS

Two Spot Blennies are generally hardy once established, but they still need clean, stable marine conditions. “Small and easy” does not mean “immune to nano tank chaos,” despite humanity’s ongoing attempt to prove otherwise with glass cubes and confidence.

Temperature: 72-78°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 allowing calmer areas for resting and perching.

DIET

Two Spot Blennies are omnivores with a herbivore-leaning diet. They naturally graze on film algae, biofilm, and tiny organisms found on rock surfaces, but they should also be offered a varied aquarium diet.

PRIMARY DIET

Frozen Food: Offer algae-rich frozen blends, enriched brine shrimp, finely chopped mysis shrimp, cyclops, marine blends, and other tiny frozen foods. We at Summit City Coral prefer frozen foods such as LRS Herbivore Frenzy and PE Mysis, chopped or broken down as needed for smaller blennies.

Prepared Herbivore Foods: High-quality herbivore pellets, spirulina flakes, marine algae pellets, and small omnivore blends can help provide balanced nutrition.

Algae-Based Foods: Nori, seaweed sheets, spirulina, algae wafers, and herbivore blends can be offered regularly. Very small pieces are best, since this fish is not exactly built like a seaweed demolition crew.

Natural Grazing: Established live rock with film algae, biofilm, and microfauna helps support natural feeding behavior. This should be viewed as supplemental, not the entire feeding plan. A Two Spot Blenny is not a free algae-control subscription with two little dots.

FEEDING FREQUENCY

Feed small amounts 1-2 times per day, with algae-based foods offered regularly. Watch body condition closely, especially in newer or very clean aquariums where natural grazing may be limited.

COMPATIBILITY

Two Spot Blennies are generally peaceful and work well in nano reefs and peaceful community aquariums. They may become territorial toward similar-shaped fish, especially other blennies or small rock-perching species in tight spaces.

COMMON TANK MATES

Fish: Small clownfish, cardinalfish, firefish, peaceful gobies, small peaceful wrasses, chromis, and other calm community reef fish.

Avoid: Other blennies in smaller aquariums, aggressive dottybacks, aggressive damsels, large predatory fish, triggers, groupers, lionfish, hawkfish large enough to eat them, and fish likely to bully or swallow them.

Same Species: Best kept singly unless the aquarium is large enough and the fish are a bonded pair. Multiple similar blennies may fight over territory.

Invertebrates: Usually safe with cleaner shrimp, hermit crabs, snails, urchins, and most common reef invertebrates.

Coral: Two Spot Blennies are generally considered reef-safe with caution. They usually ignore soft corals, LPS, SPS, zoanthids, mushrooms, and anemones, but occasional nipping can happen, especially if underfed or if the fish develops a taste for coral mucus, SPS polyps, or clam mantles.

BEHAVIORAL NOTES

Temperament: Peaceful to mildly territorial. May defend a favorite cave, perch, or section of rockwork.

Perching Behavior: Frequently rests on rocks, ledges, coral skeletons, and aquarium surfaces. Blennies often appear to “hop” around because they are not built like constant open-water swimmers.

Grazing Behavior: Spends time picking at film algae, biofilm, and tiny foods on rock and aquarium surfaces.

Reef Compatibility: Good for most reef tanks, but best listed as reef-safe with caution due to the small possibility of coral or clam mantle nipping.

Territoriality: May show aggression toward other blennies, gobies, or similarly shaped grazing fish in smaller aquariums.

Coloration: Typically pale tan to light brown with a darker facial area and two small dark spots or bars on the body. Color may shift with stress, lighting, mood, and maturity.

Nano Reef Suitability: Excellent candidate for smaller reef aquariums due to its tiny adult size, peaceful behavior, and low space requirements.

Feeding Risk: Very clean tanks may not provide enough natural grazing. Offer regular algae-based and prepared foods to keep the fish healthy.

Overflow Risk: Because of its small size, this fish may end up in overflow boxes or filtration areas if openings are not protected.

Jumping: A tight-fitting lid is recommended. Tiny blennies can still make dramatic little launch decisions if given the opportunity.

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.