Blennies are fantastic fish for your aquarium because of their unique personalities. They are very social fish that act like “dolphins in the water” and are very entertaining to watch. They love to dance, swim upside down and they also like to play with their owners.  

Blennies are very healthy and hardy fish that are great for novice aquarists or aquarists with large fish only tanks who don’t want to disturb them.  Blennies are great fish for a families first saltwater tank because they are easy to take care of and very entertaining.

Blennies are one of the most interesting kinds of fish available. Reef aquarium owners tend to shy away from these fish, though, because they’re not as common as clownfish and gobies. But many people are unaware that blennies are actually great fish for a family saltwater aquarium—especially a smaller aquarium. 

Blennies are a type of fish that can be found in tropical and subtropical waters. They’re small fish, usually between 2 and 3 inches, so they’re perfect for a nano reef or a 10-gallon aquarium.  They’re also colorful fish, making them a great addition to a dull or under-decorated aquarium.  The only downside is that they’re not as common as more well known saltwater fish.


Information about Blennies

  • Average length: 1 – 5 inches depending on variety
  • Scale Type: Most Blennies have scaleless bodies
  • Fish Colors: Blue, black, white, gray, yellow, and orange
  • Good Pet: Yes
  • Good with Other Blennies: Moderate
  • Good with Other fish species: Only peaceful ones
  • Suitable for First-Time fish Owners: Yes
  • Health Concerns: They tend to have fin rot, Marine Velvet Disease, and Marine White Spot Disease
  • Average Life Span: 2 to 6 years

Physical Appearance of Blennies

There are six sub-groups of Blennies and they differ in appearance from group to group. To understand the physical appearance of Blennies, let’s look at the most common Blennies in family aquariums.

Bicolor Blenny

The Bicolor Blenny has a dark blue color on the upper part of their body while the lower body towards the tail is orange in color. With this variety, the males tend to be larger than the females. Bicolor Blennies enjoy living in reef aquariums.

Two Spot Bimaculatus Blenny

The fish originates from the rocks and crevices of Cebu, Philippines. This Blenny has two spots near its tummy and from which its name was derived. The fish also has a black stripe on the upper part of its body and that allows it to camouflage among rocks. The Two Spot Bimaculatus Blenny has very large eyes that have a black band and a small mouth.

Horned Blenny

This fish has a dark body with some brown spots on the body and fins. The fish has some unique horns that form on its head making it a unique marine aquarium fish.

Orange Spotted Blenny

Also known as Red Spotted Blenny, this fish has a white and orange body with some orange to red spots on the side.

Starry Blenny

This Blenny is also known as Snowflake Blenny and has a dark brown body with some white spots. The tail and pectoral fins of this Blenny are yellow in color.

 Midas Blenny 

This Blenny has a golden yellow color with a blue tinge on its chin. The fish has deep blue eyes and it swims like an eel. This fish does well in a reef aquarium.

Horseface Blenny

Also known as Red Lip Blenny, this fish is dark in color with some red and yellow markings on the body. The face of the fish looks like that of a horse with a blunt nose and red lips. The head of this Blenny is also characterized by four horns.

Yellowtail Fang Blenny

The fish is also called a Forktail Blenny because the tail resembles a fork with two long spines at each end and five short spines in the middle. The body of the fish appears to be pale blue but becomes yellowish towards the tail.

Canary Blenny

This Blenny is yellow in color with a tail that looks like a fork. The fish is also known by the name Oualan Forktail Blenny and the males are larger than females. The males also tend to change their colors spontaneously during the mating season in a bid to attract the females.

Black Sailfin Blenny

This fish has a black body with equally dark fins. The fish loves perching on live reefs and is known for feeding on stubborn algae at the bottom of the tank.

Temperament of Blennies

Blennies are generally a calm fish that can live with other peaceful fish. They are a territorial fish that can fight over a mating partner or space. 

Battles between Blennies can become fatal and these fish owners should eliminate all fight triggers by keeping a good ratio of males and females in a tank. One male for every three females is a good ratio.

Having enough space in the tank is also a vital consideration for your Blennies to avoid fights due to overcrowding.

As a general rule of thumb, avoid placing more than one member of a species in a tank to avoid territorial fights. Fish from the same species of Blennies tend to fight a lot especially when there are more males in the tank.

Tank Conditions for Blennies

Blennies can adapt to any marine aquarium with optimal water conditions and enough space to swim. Blennies normally dwell at the bottom of the tank. They love habitats with lots of rocks, crevices, and hollow caves they can hide in whenever they sense danger. 

Some Blenny fish like the Lawnmower are even known to burrow themselves into the substrate.

A tank with Blenny fish should also be covered at the top because the fish are known to jump. You never want to find that they have jumped out of the tank.

The minimum tank size for a Blenny fish is about 20 gallons but some Blennies live in large tanks of 30 gallons or more. A large sized tank is ideal because water conditions don’t deteriorate fast especially with accumulation of bio waste. 

It’s important to have water testing kits to check that nitrite, nitrate, and ammonia levels remain at zero.


An aquarium filled with Blenny fish should have temperatures ranging between 77 to 81 degrees Fahrenheit. Maintaining the pH of the water for your Blennies is also crucial for the health of your fish. For Blennies, the pH is best between 8.0 and 8.4.

The pH of the water tends to fluctuate as your fish releases waste into it. You can regulate the pH by simply doing some water changes. If you find that it’s getting low it is possible to add a teaspoon of baking soda in a 20 gallon tank whenever needed. 

If the pH rises above normal, you can regulate the levels by adding a milliliter of white vinegar for every gallon of water.

Blennies are adaptable and can live comfortably in a typical aquarium environment. In the wild, they are found in coastal waters and are spread across the world. A Blenny requires a temperature range of 75 to 82 Fahrenheit. The pH level should be in the range of 8 to 8.4. These levels can vary depending upon the specific Blenny species you have in your tank.

Blenny feed on algae and for this reason, it is necessary to provide adequate light inside the tank. The light does not have to be too bright but just enough to replicate the natural sunlight. This will help to promote the growth of algae inside the tank.

Tank Maintenance

The tank would require regular cleaning as Blennies are a sensitive variety of fish. Around 25% of the water should be changed weekly. 

The levels of the water should be regularly monitored inside the tank. Any spikes can be fatal for them. The level of calcium inside the tank should not exceed 430 ppm. This will also help to maintain a stable nitrate and pH level inside the tank. 

The tank should only have a very small amount of ammonia in the water. Anything more than traces of ammonia can be toxic for the fish. You can use an all round tester kit to monitor the level of compounds and temperature inside the tank. Regularly monitor the temperature and pH level of the water inside the tank.

Best Tank mates for Blennies

Blennies are very small in size and should not be placed with large sized fish that may prey on them. Fish such as the Lionfish, Bluefish, or weakfish may even eat your Blennies. Here is a list of some fish that can live with Blennies peacefully.

Blennies that look similar in size and shape in one tank could trigger fatal battles among the fish. Blennies from different sub-groups that don’t look similar in appearance can live together in one tank.

Health Issues

Blenny fish may at times become ill especially if the quality of water in their tank deteriorates. With regular water changes and fish feed with good quality food, then the chance of diseases should be minimized. 

Here are some of the most common illnesses among Blennies.

Marine White Spot Disease

This illness is caused by a parasite called Cryptocaryon. A sick Blenny appears to have white spots on the body and the gills and the fish also seems lethargic. The fish may also have cloudy eyes and a lot of mucus production that makes the body look slimy.

Unlike freshwater White Spot Disease, you cannot increase the temperatures of the water in a marine aquarium to make it go away. A sick fish should be given copper treatment combined with water replacement in the tank. Copper can be toxic so consult with your vet about exact treatment amounts.

Increasing the salinity of the water is also known to help control the disease.

The illness is contagious and can wipe out an entire tank in a short period of time. Eliminate all stressors because stressed fish tend to contract this disease more than happy and healthy fish.

Marine Velvet Disease

Velvet Disease is caused by a parasite known as Amyloodinium ocellatum. The disease is highly contagious and kills fast if not treated immediately. An infected fish appears to have inflammation on the body and gills. 

The fish may also portray signs of lethargy and its body may become slimy due to excessive mucus production.

A sick fish should be quarantined for treatment and the rest of the tank cleaned. Copper treats the disease effectively but, the right dosage has to be followed because high concentrations of copper can kill your fish. Consult with your vet on the proper treatment of copper for your aquarium.

Fin Rot

Fin rot is a common illness among Blennies and the fins of the fish become inflamed, red, and clamped together. The disease is often caused by poor water conditions but aggressive behavior such as fin nipping can also cause the illness. A sick fish should be treated with an anti-bacterial treatment. 

The water in the tank should also be changed to maintain water quality.

Attention Requirements for Blennies

Blennies are low maintenance and good fish for beginners and experienced aquarists. The fish aren’t picky eaters and they’re resistant to diseases unless exposed to poor water conditions. 

Blennies aren’t messy fish and don’t contaminate the water in their tanks. Monthly water changes and regular replacement of water filters take much less time than other fish.

Feeding Blennies

Some Blenny fish are carnivorous while others are herbivorous and it’s important to understand what to feed your fish before leaving the pet store. 

The carnivorous Blennies can feed live or frozen foods such as bloodworms and small crustaceans. Blennies such as the Canary eat meat. The carnivorous Blennies can be fed on flakes with high protein content for proper growth and health.

The herbivorous ones are often underfed. They love grazing all day on flesh vegetables or algae growing in the tank. But often the plant materials growing in the tank are not enough for them to survive on. It is important that they have enough food to feed on throughout the day.

Some examples of herbivorous Blennies include the Lawnmower Blenny and the Bicolor Blenny. It’s also worth noting that all Blennies can be fed on fish flakes or pellets. For the herbivorous types, it is important that the flakes or pellets have a high composition of ground vegetables, vitamins, and other essential nutrients. 

It’s also easy to tell what food your Blenny can eat by observing its behavior. The Blennies that eat vegetables prefer dwelling at the bottom of the tank grazing on vegetables or live vegetation in the tank. 

Some people even use some Blenny species as cleaner fish to deal with stubborn algae growth in their aquariums. 

Carnivorous Blennies like the Fang variety of Blennies mostly swim near the surface. Even with the knowledge of how the herbivorous and carnivorous Blenny fish behave, it’s important to consult the breeder or pet store seller on what to feed your fish before taking it home.

a pile of fish flakes

Related Questions:

Is it possible to Breed Royal Grammas in a home aquarium?

Due to the territorial nature of the fish, breeding in the aquarium is difficult but not entirely impossible. In the cases where spawning occurs between a paired mate, the males create nests where the females lay eggs.

After making the nests, the males lead the females into the nests. A female can lay up to 40 eggs each day. After the eggs are laid by the females, the males pour their sperm on the eggs for fertilization. After the eggs are fertilized, hatching takes place within 4 to 5 days.

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