A tank chameleon, the Lawnmower Blenny changes intensity and color, depending on the background or even their mood!  

   Lawnmower Blennies are elongated fish that have a base color that is pale to white with 7 wide, dark vertical bars with lighter mottling.  These wide darker bars alternate with the pale to white color and they start behind the head and end at the base of the tail fin.  Depending on their mood or substrate color, the bars can be gray to brown in color and they have pale blue spots that give them the name “Jeweled Blenny.”  These chameleons can lighten the front half or the back half of their bodies depending on the background and sometimes mood.  Their single continuous dorsal fin has mottling of the same colors as the body, with the outer edge of the entire fin being orangish red.  Their other fins are clear to white. They grow to 5” and are known to live at least 6 years.  

   The Lawnmower Blenny does not have a fang or venom gland, making them a safe addition to your tank and their name gives away their obvious benefit to all marine tanks.  They eat large amounts of algae, in fact, any algae including macro algae!  There are a few others in their genus that have similarities, however the single continuous dorsal fin and 5” size sets it apart from others that are much larger or smaller.  These little mowers will leave kiss marks all over the tank’s glass as they rasp off the algae with their comblike teeth, however they are just as happy munching on macro algae.

   These landscapers are great for the beginner aquarist who has a matured tank that is growing plenty of algae.  These little fish are easy to keep as long as they have plenty of food.  Growing macro algae in a separate tank can be added to supplement their diet if the algae population drops.  Although they are disease resistant, any fish can fall victim to bacterial infections or parasites if the water quality is low.

   House with peaceful fish in a tank that does not have any other fish competing for algae, unless the tank is over 55 gallons.  They will be eaten by larger fish like groupers, lionfish, frogfish, toadfish, anglerfish, etc.  Aggressive fish should be avoided.  Damselfish that are algae eaters should also be passed up as a potential tank mate, since these territorial fish will attack anything eating their “algae crop” and a Lawnmower Blenny stands no change in such a fight.

    The minimum tank size is 55 gallons, however if adding other algae eaters, tank should be 75 gallons or more.  Add enough light to promote algae growth.  They can tolerate steady temperatures from 75 to 84˚F.  Although they are found in estuaries in the wild, they should not be kept in a brackish water tank.  In the wild, Lawnmower Blennies do not stay in brackish water for too long, only entering to find plants to feed on.  They like the bottom section of the tank and water movement shouldn’t be too swift down there.  

   The Lawnmower Blenny’s appearance gives it an adorable charm to go along with a great personality. This along with algae being its prime food source, make this fish an excellent addition to a peaceful reef aquarium.

For more Information on keeping this fish see:
Guide to a Happy, Healthy Marine Aquarium

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Perciformes
  • Family: Blenniidae
  • Genus: Salarias
  • Species: fasciatus
Lawnmower Blenny – Quick Aquarium Care
  • Aquarist Experience Level: Beginner
  • Aquarium Hardiness: Very Hardy
  • Minimum Tank Size: 55 gal (208 L)
  • Size of fish – inches: 5.0 inches (12.70 cm)
  • Temperament: Peaceful
  • Temperature: 75.0 to 84.0° F (23.9 to 28.9&deg C)
  • Range ph: 8.0-8.3
  • Diet Type: Herbivore
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Habitat: Distribution / Background

   The Lawnmower Blenny, Salarias fasciatus was first described by Bloch in 1786.  The most common names are Banded Blenny, Banded Jeweled-Blenny, Barred Blenny, Jeweled Blenny, Jeweled Rockskipper, Lineated Blenny, Lined Blenny, and Painted Blenny.  The three most commonly used non “official” names are Lawnmower Blenny, Algae Blenny, and Sailfin Blenny. 

   The Lawnmower Blenny is found in the Indo-Pacific from the Red Sea and East Africa, then to Samoa and northward to the Ryukyu Islands.  They are found south from there to the Great Barrier Reef and New Caledonia where they are predated on by the Leopard Coral Grouper (Plectropomus leopardus).  Searching for anything green, they are found on reef flats, shallow lagoons, seaward reefs, and in estuaries where there is plenty of algae and in areas of rubble patches, reef flats and reef slopes.  They are solitary fish, found at depths up to 262 feet (0 to 8 meters), feeding on mainly on various types of aquatic plants, algae and detritus.  

   The Lawnmower Blenny is on the IUCN Red List for Least Concerned with a stable population trend with no known major threats.

   There are many similarities between the blennies in the Salarias genus, with many of them inhabiting the same waters as the 5” Lawnmower Blenny.  A few of them are:

  • White-Spotted Blenny (Salarias alboguttatus):  Similar light and dark blotching, however the white spots and smaller size of 3.5” set it apart from the Lawnmower Blenny.
  • Seram Blenny (S. ceramensis):  The Seram Blenny is larger, reaching almost 6” but are very similar in color with the exception of a good sized black circle or dot in the middle front of the body, just above and behind the pectoral fin.
  • Breast-spot Blenny (S. guttatus):  This blenny has 2 dorsal fins and can have reddish orange spots that run along the base of the dorsal fin and only reaches 3.9.”  
  • Scientific Name: Salarias fasciatus
  • Social Grouping: Solitary
  • IUCN Red List: LC – Least Concern – Stable population trend.


   The Lawnmower Blenny has an elongated body and can vary it’s color intensity depending on substrate or rock coloring, as well as stress.  They have one continuous dorsal fin that can be tipped in orangish red and mottled with pale tan to cream, with brown speckling.  The eyes have brown and cream speckling around the pupil that blends in with the speckling of the body.  The tail fin and pectoral fins are clear to opaque, and the pelvic fins, which they use to balance when resting are white.  The body is pale to white with 7 thick, dark, vertical bands that alternate with a lighter color.  These darker bands can be gray to brown, with lighter mottling on them and these alternate with the lighter body color.  The blenny can make the first 1/2 of it’s body very light, making the bars toward the front very pale, or they can make the back half pale.  Their anal fin is interesting, having the first several rays or spines grow longer which typically are the males.  Their belly is usually so full they almost “roll” on it as they sit around the tank.  The Lawnmower Blenny grows to 5” and has been known to live up to 6 years in captivity, typically in larger tanks with plenty of algae growth.

  • Size of fish – inches: 5.0 inches (12.70 cm)
  • Lifespan: 6 years – Several aquarists stated they have had their Lawnmower Blenny from 5 to 6 years, typically in larger tanks.

Fish Keeping Difficulty

   The tank should be at least 55 gallons with no other algae eaters in the tank to compete for food.  Lawnmower Blennies are herbivores and should not be fed meaty foods.  Similar to other fish, feeding them inappropriate foods may shorten their lives considerably.  The water should be matured and there should be plenty of algae to keep your blenny full.  His belly should always look rounded, which means he is eating well.  Feed all your herbivores first so they do not eat any meaty foods that are intended for your carnivores.  Do not house with aggressive fish or fish that are large enough to swallow them.  Supplement their algae with spirulina and foods for herbivores.  Growing caulerpa or chaetomorphia in another tank to supplement their diet can be helpful to ensure they eating well.

  • Aquarium Hardiness: Very Hardy – If there is enough to eat.
  • Aquarist Experience Level: Beginner

Foods and Feeding

   Lawnmower Blennies are herbivores, according to the stomach contents at fishbase.org.  Although some literature may say they eat meaty things, they actually are not omnivores and may not live more than a few years with too much meaty food in their diet.  They get very used to prepared foods and will happily eat whatever you put in so feed your herbivores first.  Feed flake or pellet for herbivores along with the frozen prepared herbivore foods.  Also grow Chaetomorphia and/or Caulerpa in another tank or the sump to supplement their diet.  

  • Diet Type: Herbivore – No meaty foods should be purposely fed to them.
  • Flake Food: Yes – For herbivores.
  • Tablet / Pellet: Yes – Sinking and for herbivores.
  • Vegetable Food: All of Diet – Feed herbivores first.
  • Feeding Frequency: Several feedings per day

Aquarium Care

Reef tanks:

  • Medium sized up to 90 gallons, perform 15% bi-weekly. 
  • Large Tanks 100 gallons and over, once water is aged and stable can be changed 10% bi-weekly to 20% monthly, depending on bioload.

Fish only tanks:*

  • Medium sized up to 90 gallons, perform 20% to 30% monthly depending on bioload. 
  • Large Tanks 100 gallons and over, once water is aged and stable can be changed 20% to 30% every 6 weeks depending on bioload.

For more information on maintaining a saltwater aquarium see: Saltwater Aquarium Basics: Maintenance. A reef tank will require specialized filtration and lighting equipment. Learn more about reef keeping see: Mini Reef Aquarium Basics.

*Note:  If this is the ONLY fish in the tank, with no corals or other fish you can get away with less water changes of 20% monthly.

  • Water Changes: Bi-weekly

Aquarium Setup

   Tank needs to be at least 55 gallons, and it should be mature and growing plenty of algae.  Do not have any other herbivores in this smaller tank that also feeds on any plants or algae.  Their need for large amounts of algae eliminates any nano tank.  Keeping them with other algae eaters equals a much larger tank, or they can starve to death.  Any substrate or rock is fine, as long as it is lots live rock to provide surface area that algae can grow on and a few places to hide.  Provide enough light to promote lots of algae growth. Lawnmower Blennies can tolerate temperatures from 75 to 84˚F (24-29˚C), normal pH and salinity; typical for all saltwater fish.  Although they are found in estuaries, this is not a place they stay in for very long, so do not house them in brackish water.  Nothing special is needed when it comes to water movement, though they prefer the bottom areas of the tank which should not have a blast of water tumbling your rolly polly Lawnmower Blenny around in the sand!  There’s a visual!

  • Minimum Tank Size: 55 gal (208 L) – No other algae eaters in this size tank.
  • Suitable for Nano Tank: No
  • Live Rock Requirement: Typical Amount
  • Substrate Type: Any
  • Lighting Needs: Moderate – normal lighting – Enough to promote algae growth.
  • Temperature: 75.0 to 84.0° F (23.9 to 28.9&deg C)
  • Breeding Temperature: – unknown
  • Specific gravity: 1.023-1.025 SG
  • Range ph: 8.0-8.3
  • Brackish: No
  • Water Movement: Any – Avoid powerful water movement at the bottom where they feed.
  • Water Region: Bottom

Social Behaviors

   Lawnmower Blennies are peaceful little fish; however, if there are two males or two females in a tank under 100 gallons, (under 6 feet long) they will fight to the death.  A known and paired male and female may be attempted in a 100+ gallon tank to ensure there is enough to eat for both of them.

   Do not house with others from the same genus or with other algae eaters that can out compete them for food in the minimum tank size of 55 gallons.  In larger tanks, over 100 gallons or more, other algae eaters like tangs and angels may be added as long as there is enough light and surface for algae to grow on.  They do not bother any other fish, unless they look similar or if they feel they need to compete for algae.  They are great in a peaceful to semi aggressive tank, and will mind their own business.  Do not house with very aggressive fish like triggers or large fish that can swallow them whole like groupers, lionfish, toadfish, most anglers and all frogfish.  Avoid aggressive damselfish that are also algae eaters since they are territorial and will attack your Lawnmower Blenny, especially once they are full grown.  Large dottybacks should only be kept in the same tank if the tank is very large.

   In a reef setting, they are typically well behaved, however at times they have been said to nip at Large Polyp Stonies.  Being an herbivore, it may be more likely they are eating the algae on the hard part of the coral and getting some of the polyp with it.  Seems logical, however a starved fish may sample anything!  

   Inverts such as clams are safe, with the Lawnmower Blenny doing it the favor of removing algae from the hard base of the clam.  Other inverts are safe.  

  • Venomous: No
  • Temperament: Peaceful
  • Compatible with:
    • Same species – conspecifics: Sometimes – Singly unless a known bonded male and female pair in a tank that is at least 100 gallons.
    • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Safe
    • Semi-Aggressive (anthias, clownfish, dwarf angels): Monitor – Avoid housing with dwarf angels that are heavily reliant on algae in a 55 gallon tank.
    • Monitor – Do not house with damselfish who are algae eaters as they are too aggressive. Keep an eye on large dottybacks.

    • Large Semi-Aggressive (tangs, large angels, large wrasses): Monitor – Some angels that are more aggressive may pick on the blenny. Only add tangs if tank is at least 6 feet long.

    • Large Aggressive, Predatory (lionfish, groupers, soapfish): Threat
    • Safe
    • Anemones: Safe
    • Mushroom Anemones – Corallimorphs: Safe
    • LPS corals: Monitor – Some have stated they may nip on LPS, however it is more likely they are eat the algae on the hard part of the coral.
    • SPS corals: Safe
    • Gorgonians, Sea Fans: Safe
    • Leather Corals: Safe
    • Soft Corals (xenias, tree corals): Safe
    • Star Polyps, Organ Pipe Coral: Safe
    • Zoanthids – Button Polyps, Sea Mats: Safe
    • Sponges, Tunicates: Safe
    • Shrimps, Crabs, Snails: Safe
    • Starfish: Safe
    • Feather Dusters, Bristle Worms, Flatworms: Safe
    • Clams, Scallops, Oysters: Safe
    • Copepods, Amphipods, Mini Brittle Stars: Safe

Sex: Sexual differences

   Females have 2 spines on the anal fin, with one spine being smaller or embedded near the body.  Males also have 2 anal spines, however they are longer and both are capped with fleshy tissue.  

Breeding / Reproduction

   Females will lay their demersal eggs on the substrate and males will fertilize and guard them until they hatch.  These eggs stick to the substrate with a filamentous adhesive pedestal or pad and when they hatch they become planktonic and inhabit shallow coastal waters as larvae.  

   They have not been bred in captivity to date. (Jan 2015)

  • Ease of Breeding: Unknown

Fish Diseases

   Lawnmower Blennies are pretty much disease resistant.  There are no special directions for treating them with common illnesses, however, do not treat them with medicines that are dangerous for scaleless fish. 


   These algae munchers are easy to find online and in store and start around $15.00 USD (Jan 2015).





By Scott W. Michael

T.F.H. Publications

Copyright © 2001 by T.F.H. Publications, Inc.



By Scott W. Michael

T.F.H. Publications

Copyright © 2005 by T.F.H. Publications, Inc.





Lawnmower Blenny

Salarias fasciatus

© 2004-8 Aquaticcommunity.com

URL: http://www.aquaticcommunity.com/blennies/LawnmowerBlenny.php