QUICK STATS

Care Level: Easy to Moderate
Diet: Herbivore / Omnivore
Temperament: Peaceful, May Be Territorial Toward Similar Fish
Reef-Safe: Yes
Approximate Purchase Size: 2-4"
Approximate Max Size: Around 5"
Recommended Tank Size: 30 Gallons or Larger

ALGAE BLENNY

The Algae Blenny (Salarias fasciatus), also commonly called the Lawnmower Blenny, is a hardworking and entertaining saltwater fish known for its constant grazing behavior, expressive face, and absolute refusal to look normal in a photograph. This fish spends much of its day hopping across rockwork, perching on surfaces, and picking at microalgae throughout the aquarium.

Algae Blennies are popular for established reef tanks because they are generally hardy, peaceful, and reef-safe. They can help graze on film algae and other soft algae growths, but they should not be treated as a complete algae-control plan. They are fish, not unpaid aquarium interns with dental tools.

This species does best in mature aquariums with plenty of live rock and natural algae growth. In newer or overly clean tanks, they may struggle to find enough natural grazing material, so supplemental feeding is important.

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 an Algae Blenny. While they are not constant open-water swimmers, they do need enough rockwork and surface area to graze, perch, and establish a comfortable territory. Multiple aquarium care sources list a 30-gallon minimum and a max size around 5 inches for Salarias fasciatus.

HABITAT RECOMMENDATIONS

Algae Blennies do best in mature aquariums with live rock, stable water quality, and natural algae growth.

Aquascaping: Provide plenty of live rock with caves, ledges, and open grazing surfaces. They enjoy perching and hopping from spot to spot like tiny judgmental reef gargoyles.

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

Rockwork: Established live rock is highly recommended. The more surfaces available for grazing, the better.

Tank Maturity: A mature aquarium is strongly preferred. New tanks may not have enough algae or biofilm to support natural grazing.

Tank Cover: A tight-fitting lid is recommended. Blennies are not always the worst jumpers, but fish are famous for turning tiny gaps into crime scenes.

WATER PARAMETERS

Algae Blennies are considered hardy once established, but they still require clean, stable saltwater conditions. “Hardy” does not mean “place in chaos and hope,” despite humanity’s repeated experiments.

Temperature: 72-78°F
pH Level: 8.1-8.4
Salinity: 1.020-1.025 specific gravity
Alkalinity: 8-12 dKH
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: Moderate water movement is ideal. Good flow helps move waste toward filtration while still allowing the blenny to perch and graze comfortably.

DIET

Algae Blennies are primarily herbivorous grazers, though they may accept a variety of prepared foods. In the aquarium, they spend much of their time scraping and picking at algae and biofilm from rockwork, glass, and other surfaces. They should still be offered supplemental foods, especially once natural algae becomes limited.

PRIMARY DIET

Natural Grazing: Algae Blennies graze on film algae, soft algae growth, and biofilm throughout the aquarium.

Shop Favorite: Our favorite food to offer is Herbivore Frenzy by LRS because it provides a strong variety of herbivore-focused marine ingredients and helps support fish that need more plant-based nutrition.

Algae-Based Foods: Offer nori, spirulina flakes, herbivore pellets, and algae wafers. Attach seaweed sheets to a clip or rock so the blenny can graze naturally.

Prepared Foods: High-quality marine pellets or flakes may be accepted, especially formulas made for herbivores or omnivores.

Frozen Food: Occasional mysis shrimp, enriched brine shrimp, or mixed marine foods can be offered for variety, but algae-based foods should remain the main focus.

FEEDING FREQUENCY

Feed small amounts 1-2 times per day, especially in tanks without heavy natural algae growth. A blenny with no algae and no supplemental food is not “cleaning the tank,” it is slowly regretting everyone’s decisions.

COMPATIBILITY

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

COMMON TANK MATES

Fish: Clownfish, cardinalfish, wrasses, firefish, tangs, dwarf angelfish, peaceful damsels, and other community reef fish.

Avoid: Other algae blennies or similarly shaped bottom-perching fish in smaller aquariums unless the tank is large enough with plenty of territory.

Invertebrates: Safe with most cleaner shrimp, hermit crabs, snails, urchins, and other common cleanup crew animals.

Coral: Algae Blennies are considered reef-safe and generally do not bother soft corals, LPS, SPS, zoanthids, mushrooms, or anemones. Some sources note that stressed or underfed individuals may occasionally nip at coral polyps, so regular feeding still matters. Because apparently even reef-safe fish have footnotes.

BEHAVIORAL NOTES

Temperament: Peaceful overall, though they may defend their favorite perching and grazing areas.

Algae Control: Helpful for grazing film algae and soft algae growth, but not a complete solution for severe algae problems.

Personality: Often very visible once settled, with a goofy perching behavior and expressive face that looks mildly disappointed in your aquascape.

Reef Compatibility: Excellent for most reef tanks. They usually ignore coral and invertebrates.

Territoriality: May act aggressively toward other blennies or similar-shaped fish.

Jumping: A tight-fitting lid is recommended. The fish may look like it belongs on a rock, but it can still make terrible aerial choices.

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, use a net or specimen container to gently transfer the fish into the aquarium. 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.