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Blenny Care Sheet

Developed with and approved by a qualified veterinarian.

Blenny

This care sheet covers a variety of blennies, including:

  • Lawnmower blenny
  • Bicolor blenny
  • Fang blenny 
  • Tail-spot blenny
  • Canary blenny
  • Midas blenny
  • Panamic barnacle blenny 
  • Starry blenny
  • Forktail blenny
  • Harptail blenny

 

Overview 

Salaris fasciatus, Ecsenius bicolor, Melacanthus grammistes, Ecsenius stigmatura, Melacanthus oualanensis, Ecsenius midas, Acanthemblemaria hancocki, Salarias ramosus, Melacanthus atrodorsalis, Melacanthus mossambicus

Blenny species are found in many areas of the world, from the tropical Indo-Pacific to the Atlantic Ocean. These close relatives of gobies are intelligent, entertaining and rather territorial.   Some will burrow into the substrate or scoot around the bottom of the aquarium, hiding in crevices amongst live rock. Some blennies, like the fang blenny, have recurved canine teeth containing venom, which they use for defense and protecting their territory. Blennies come with varying temperaments, and it is always best to research your specific species to understand compatibility with other marine aquatic life.

 

Typical appearance and behavior 

  • Some can be territorial and need plenty of hiding places; they especially like to hide in holes and crevices within live rock 
  • Several species can only swim a short distance at a time, so it looks like they’re hopping, rather than swimming 
  • They usually inhabit the bottom of the tank, hanging out on the substrate or perching on a rock 
  • Some blennies can play dead when they feel threatened 
  • Some species are venomous and can deliver a painful bite 

 

Characteristics 

Care Difficuty Beginner to intermediate
Average Life Span Up to 5+ years with proper care, depending on species 
Average Adult Size Up to 6+ inches long, depending on species
Diet Omnivorous, herbivorous and carnivorous depending on species
Minimum Habitat Size 10+ gallons, depending on species
Water temperature 74–80°F
Specific gravity 1.020–1.025

 

Habitat 

Habitat size

A minimum of 10+ gallons is recommended for juvenile or small species like the barnacle blenny; however, water conditions can change rapidly in smaller water volumes. A larger aquarium is always recommended for adult or larger blenny species.

Building your habitat

  • Water health
    • Provide proper filtration to ensure optimal water quality to help maintain health   
    • Provide moderate to strong water circulation, based on species, to mimic water currents found in the blenny's natural habitat 
    • Stable water quality (pH, ammonia, nitrate, nitrite) and water temperature are critical to the health of aquatic life; if you are unsure of your water quality, bring a sample to Petco for free testing 
    • A protein skimmer can help maintain great water quality and high dissolved oxygen levels 
    • An aquatic heater should be used to stabilize water temperature, ensuring it does not fluctuate more than +/-2 degrees in a 24-hour period 
    • The specific gravity should remain stable; do not allow specific gravity to fluctuate more than +/-0.001 in a 24-hour period  
  • Décor
    • Provide rock and décor for hiding places and plenty of room for movement
  • Live rock
    • This can provide a natural food source and hiding places while also enhancing biological filtration.

 

Feeding 

A well-balanced blenny diet consists of: 

  •  
  • Flakes, pellets, freeze-dried and frozen foods 
  • Herbivores should be provided with algae sheets and wafers 
  • Varied food to ensure proper nutritional balance 

Things to remember when feeding your blenny:  

  • Feed 1–2 times daily, no more than fish can eat in 1–2 minutes 
  • Thaw frozen food before feeding

 

Blenny care 

  • Maintaining great water quality with regular water changes and adequate filtration is important to help keep your blenny healthy 
    • Daily: Check filter, water temperature and other equipment 
    • Weekly: Test water quality at least once a week 
    • Weekly to monthly: Change 10–25% of the total volume of water every 2–4 weeks, or as needed; change filter media monthly 
  • Avoid overcrowded conditions, which are a major cause of stress and disease 

 

Where to buy blennies

Blennies are available for purchase at Petco online and in-store; availability varies by location. If visiting your local Petco Pet Care Center location, please call ahead to check availability. 

 

Supplies  

 

Tank mates 

  • Introduce new inhabitants to the aquarium gradually 
  • Most blennies are peaceful, but temperament can vary; they may be compatible with: 
  • Anthias 
  • Basslets 
  • Butterflyfish 
  • Dragonets  
  • Dwarf and large angelfish 
  • Cardinalfish 
  • Clownfish 
  • Damselfish 
  • Filefish
  • Foxface/rabbitfish 
  • Gobies 
  • Hawkfish  
  • Pseudochromis 
  • Tangs
  • Unless kept in a breeding pair, keep only one blenny per aquarium 
  • Introduce new inhabitants to the aquarium gradually 

 

Health  

Signs of a healthy blenny 

  • Clear eyes  
  • Eats vigorously  
  • Fins completely intact and undamaged 
  • Bright, even coloring 
  • Free of parasites or disease 

Red flags (if you notice any of these signs, contact your local aquatic specialist or aquatic veterinarian) 

  • Loss of color or appetite 
  • Spots or fungus on body or mouth 
  • Cloudy eyes or pop-eye 
  • Frayed fins 
  • Labored breathing 
  • Erratic swimming 
  • Weight loss 
  • Bloating 
  • Listlessness  

 

Common blenny health issues

Health Issue Symptoms or Causes Suggested Action
Health IssueFin rot Symptoms or CausesFrayed or disintegrating fins; the base of the fins usually reddens. Suggested ActionImprove water quality; consult your local aquatic specialist or aquatic veterinarian for treatment.
Health IssueFungus Symptoms or CausesWhite cottony growth and/or discoloration of the eyes Suggested ActionQuarantine fish; use a commercial antifungal remedy as directed
Health IssueBacterial infections Symptoms or CausesCloudy eyes, open sores and/or reddening of the skin Suggested ActionImprove water quality; use a commercial antibacterial remedy as directed, consult your local aquatic specialist or aquatic veterinarian for treatment.
Health IssueMarine ich or velvet Symptoms or CausesCysts on fins, gills and skin; labored respiration, excess skin mucus or pale skin. Suggested ActionQuarantine fish immediately and use a commercial parasite remedy; complete a water change; freshwater dips can dislodge the parasites; consult your local aquatic specialist or aquatic veterinarian for treatment.
Health IssueViral infection (lymphocystis) Symptoms or CausesWhite nodule growths on fins or body. Suggested ActionImprove water quality; consult your local aquatic specialist or aquatic veterinarian for treatment.

 

FAQs 

  • What do lawnmower blennies eat? Lawnmower blennies are herbivores who feed primarily on algae; their diet should be supplemented with algae sheets or wafers. 
  • What do blenny fish eat? A blenny’s diet will vary based on species. Some blennies are herbivores, while others are omnivores. Depending on species, they can be provided a variety of flakes, pellets, freeze-dried and frozen foods. Herbivores should be provided algae sheets and wafers.  
  • What are blennies? Blennies are a diverse group of fish. They are typically a smaller, slender, elongated fish species with long dorsal fin. 

 

Additional care sheets

Notes and resources

Ask a Pet Care Center associate about Petco's selection of products available for the care and happiness of your new pet. All products carry a 100% money-back guarantee.

Because all aquatic life are potential carriers of infectious diseases, such as atypical mycobacterium and salmonella, always wash your hands before and after handling your aquatic life or habitat contents to help prevent the potential spread of disease.

Pregnant women, children under the age of 5, senior citizens and people with weakened immune systems should contact their physician before purchasing or caring for aquatic life and should consider not having aquatic life as a pet. 

Go to cdc.gov/healthypets for more information about aquatic life and disease.

The information on this care sheet is not a substitute for veterinary care. If you need additional information, please contact your veterinarian as appropriate.