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Fish Profile: The Lawnmower Blenny (Salarias fasciatus)

The lawnmower, jewelled, sailfin, or algae blenny was first described to western science by Marcus Eleiser Bloch in 1786. Bloch was a German physician and prolific ichthyologist. He held one of the largest fish collections of his time and published a 12 volume encyclopedia of the fishes of Germany, Africa, and Australasia.


Salarias fasciatus is a small combtooth blenny of the family Blenniidae. They reach a maximum standard length of approximately 5.5 inches.

This species evolved to blend in with surrounding rocks, coral, and rubble. Its base color is a light tan or beige beset with dusky brown bands, numerous pale spots, and dark streaks. S. fasciatus can even alter the vividness and intensity of its coloration to further blend in with its surroundings.

It appears long with vertically oriented pectoral and pelvic fins to manipulate its position when perched on rocks.

This species is a joy to watch as it swims about the aquarium. It has lots of personality and seems to become transfixed with onlookers, using its large, orbital eyes to survey its surroundings.


S. fasciatus is distributed throughout the Red Sea, the Indian Ocean, and the Pacific Ocean. This species has a relatively wide distribution.


S. fasciatus spends most of its time grazing amongst rubble patches, reef flats, coral outcrops, weedy areas, slopes, mixed coral, and sand. Most commonly found in shallow lagoons, seaward reefs, and estuaries rich in algae and detritus.

S. fasciatus mostly inhabits depths between intertidal (sometimes exposed to air) and up to eight meters.

Aquarium Habitat

In the aquarium, S. fasciatus is comfortable with non-grazing species outside of its family (blenniidae). If your tank is small enough, S. fasciatus is known to chase away similar sized grazing blennies (Townsend 2004). Practice caution when placing conspecifics (two of the same species) together in a smaller tank. Usually only mating pairs get along. This species is a quick swimmer, and blends well with its environment, making it a difficult species to pick on.

Its captive environment should be replete with caves, outcroppings, shelves, and overhangs formed from plenty of live rock. There should also be at least a third to half of the sand bed exposed. S. fasciatus will explore the entire tank and feel most comfortable when there are plenty of spaces to safely retreat to. It will spend most of its time on the rock or sand bed, grazing on algae.

Most aquarists suggest waiting to add S. fasciatus until your tank is established and has a variety of algae growing. S. fasciatus is primarily a detritivore and will consume other particles beside algae, but an established tank is the best way to provide both food types.


If you don’t have enough algae growing, or your sand bed is too clean, you can add nori sheets or dried seaweed to supplement. Nori sheets are excellent sources of plant material for all your herbivores including tangs, some invertebrates, blennies, and others. You can attach a piece of nori or dried seaweed to a clip with a suction cup attached and suction it to the inside glass of your aquarium once daily. The size of the piece added is determined by how many herbivores you have. Also consider the placement of the sheet. If you have bottom inhabiting (benthic) herbivores, make sure the sheet is attached near the sand bed.

Aquarium Water Parameters

S. fasciatus enjoys the normal water parameters of an Indo-Pacific environment. Keep the pH around 8.0 with the alkalinity between 7.3 and 12 depending on your particular system. Water temperature should be stable between 73 and 77 degrees.


S. fasciatus has low sexual dimorphism, meaning it is difficult to discern males from females. One physical characteristic that does differ amongst the sexes are the elongated spines of the anal fin in males compared to females (Awata 2010).

Wild populations off the coast of Okinawa, Japan breed between the months of April and June. This may suggest cooler waters can instigate breeding (Awata 2010).

Male S. fasciatus will defend a nest dug into the sand, rubble, or cave. Like most blennies, S. fasciatus is polygynous, meaning multiple females may lay eggs in the nest. Only the males will defend and rear the eggs to hatch (Awata 2010).

In the wild, smaller, parasitic males are known to mimic female mating coloration, sneak into stronger males’ nests and attempt to fertilize some of the eggs (Awata 2010).

Grazing and Young Corals

As combtooth blennies, S. fasciatus regularly graze algae on rocks and substrate in the aquarium. What does that mean for the corals attached to these rocks? Is there any damage done to the polyps of these corals by the blennies’ constant grazing?

A 2008 study published in the journal Coral Reefs attempted to answer this question. They set out to determine the effects of grazer disturbance on young corals and determine at what stage or development corals were no longer damaged by grazing disturbance.

They began by applying an algal matrix and coral recruits (single and multi polyp young corals) to an artificial substrate. They introduced S. fasciatus and recorded the damage to corals as the fish grazed.

They determined that blennies, despite being small and having diminutive dentition (teeth), can negatively affect the survival of young coral recruits. They also found that when corals reach a certain size (6 - 8 polyps) they can resist most damage from grazing activity.

In your aquarium, this means most of your corals will be just fine. However, if you frag out older corals or introduce young, single polyp recruits, keep an eye on them as your S. fasciatus grazes indiscriminately.

Clean up Crew

S. fasciatus is an excellent addition to an appropriately sized, established reef aquarium. They are peaceful, exciting to watch, and are excellent grazers. If your tank is fairly new (less than 6 months) and experiencing algae problems, consider testing for nutrient levels and lowering them before adding a grazing blenny. If your algae is caused by elevated nutrients, an additional fish will increase the bioload. Even though the new inhabitant eats algae, it may detrimentally contribute to the algae problem overall.


7.8 - 8.2


7.3 - 12


73 - 77 degrees Fahrenheit

Preferred Lighting

Low - High

Maximum Length

5.5 inches

Tank Size

40 U.S. Gallon


Aggressive toward blennies, peaceful toward other species.

Literature Cited

Awata, S. et. al. 2010. “Seasonal changes in reproductive and physical condition, sexual dimporphism, and male mating tactics inthe jewelled blenny Salarias fasciatus.” Ichthyological Research. 57:161-168.

Christiansen, N.A., Ward, S., Harii, S., & Tibbetts, I.R. 2008. “Grazing by a small fish affects the early stages of a post-settlement stony coral.” Coral Reefs. 28:47-51.

Townsend, K.A., & Tibbetts, I.R. 2004. “The ecological significance of the combtoothed blenny in a coral reef ecosystem”. Journal of Fish Biology. 45:77-90.


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