Lawnmower Blenny

The Algae Lawnmower Blenny, also known as the Sailfin Blenny or Jewelled Blenny, is a characterful saltwater fish with a mottled olive, tan, gray, and brown body marked by irregular bands, pale spots, and occasional blue highlights. Branched cirri above the eyes, expressive facial features, and an elongated dorsal fin give this bottom-dwelling marine aquarium fish a distinctive appearance. Its natural camouflage allows it to blend easily into live rock and reef rubble. 

Native to the Indo-Pacific, Salarias fasciatus ranges from the Red Sea and East Africa to Samoa, north to the Ryukyu Islands, and south to the Great Barrier Reef and New Caledonia. It inhabits shallow reef flats, lagoons, seaward reefs, and algae-rich rubble areas, where it lives primarily as a solitary grazer. Adults reach approximately 5.5 inches. 

Its active grazing, unusual perching behavior, and engaging personality make it a popular addition to mature reef aquariums and peaceful fish-only aquariums. Although it can help manage certain algal films and filamentous growth, it will not consume every nuisance-algae species and should not be treated as a substitute for proper nutrient control and aquarium maintenance. 

Quick Care Guide

Care Level: Easy to Moderate
Minimum Tank Size: 30 gallons
Temperament: Peaceful
Diet: Herbivore / Detritivore
Reef Safe: Yes
Region: Indo-Pacific, from the Red Sea and East Africa to Samoa
Scientific Name: Salarias fasciatus 

Tank Requirements

Provide a mature aquarium with abundant live rock, established algal growth, and numerous caves, ledges, and crevices. The Algae Lawnmower Blenny spends much of its time perched on rockwork before making short movements to graze nearby surfaces. Arrange the aquascape so the fish has several secure retreats and broad areas of exposed rock available for feeding. 

A sand or fine-gravel substrate is suitable, although no specialized substrate is required. Moderate, well-distributed water movement and good oxygenation are appropriate, with calmer areas available among the rocks. The aquarium should be well established rather than newly cycled, as sterile rockwork may not provide enough natural grazing material.

Use a securely fitted lid or mesh cover. This species may jump when startled, pursued, or newly introduced. Long-term housing should provide enough rock surface and territory for its adult size rather than relying only on aquarium volume. 

Diet and Feeding

In nature, Salarias fasciatus feeds by scraping algae and associated organic material from rocks, coral rubble, and other hard surfaces. Captive specimens commonly graze microalgae, soft filamentous growth, and biofilm, but individual feeding preferences vary. They should not be expected to eliminate all forms of hair algae, cyanobacteria, or other nuisance growth. 

Supplement natural grazing with spirulina-based flakes, marine herbivore pellets, frozen algae blends, finely chopped marine algae, and small pieces of nori. Occasional mysis shrimp, enriched brine shrimp, or mixed marine frozen foods may be accepted, but algae-rich foods should remain the foundation of the diet.

Offer one or two small meals daily and monitor body condition closely. Some individuals adapt readily to prepared foods, while others depend heavily on naturally growing algae. A blenny with a noticeably pinched abdomen may not be receiving enough nutrition, even when it appears to graze throughout the day. 

Temperament and Tankmates

The Algae Lawnmower Blenny is generally peaceful toward unrelated community fish but may become territorial around its preferred cave and grazing area. Suitable tankmates include clownfish, cardinalfish, gobies, peaceful wrasses, dwarf angelfish, and other non-predatory marine species.

Keep one specimen in most aquariums. It may behave aggressively toward other lawnmower blennies, combtooth blennies, or similarly shaped bottom-dwelling fish. Competition may also develop with tangs and rabbitfish that graze the same rock surfaces, particularly when food or territory is limited.

Avoid highly aggressive tankmates that may prevent it from feeding or repeatedly force it away from the rockwork. Newly introduced specimens may remain hidden until they become familiar with the aquarium.

Reef Compatibility

The Algae Lawnmower Blenny is considered reef safe. It does not normally consume healthy stony corals, soft corals, anemones, clams, snails, or ornamental shrimp. Its grazing is generally directed toward algae and biofilm growing on rocks, aquarium walls, and other hard surfaces. 

The fish may perch on coral colonies or scrape algae from frag plugs and exposed coral bases. This activity is usually harmless, although loosely mounted fragments may be disturbed. Decorative macroalgae may also be grazed.

Water Parameters

Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Maintain consistent salinity, good oxygenation, and stable water quality. Stability is more important than repeatedly adjusting the aquarium to reach one exact reading.

Common Considerations

• Provide mature rockwork: Established algae and biofilm are important for natural grazing.

• Do not rely on algae control alone: This species does not consume every nuisance-algae type.

• Monitor body condition: Constant grazing does not guarantee that the fish is receiving enough nutrition.

• Use caution with other blennies: Territorial disputes are common with similar-looking or competing grazers.

• Secure the aquarium: A fitted lid helps prevent jumping when the fish is startled.