Blue Eyed Damselfish “Plectroglyphidodon Johnstonianus”

blue eyed damselfish

Last updated on August 4th, 2022 at 03:41 am

The blue eyed damselfish is a type of fish that can be found in the Pacific and Atlantic oceans. They are small fish, typically measuring around four inches in length. What makes these fish unique is their bright blue eyes.

The blue eyed damselfish is a very common fish found in the Indian Ocean. They are usually brown, blue, or green with yellow fins and blue eyes. Damselfishes are omnivores, meaning they will eat both plants and animals. Usually, their diet consists of algae, seaweed, small crustaceans like shrimp or krill, planktonic organisms that live near the surface of the water column such as jellyfish eggs and larvae.

They are popular aquarium fish due to their attractive coloring and playful personality. They are generally considered to be hardy fish and can tolerate a wide range of water conditions.

Blue eyed damselfish make a great addition to any saltwater aquarium and are sure to add color and excitement to your tank. If you’re looking for an interesting fish that is sure to turn heads, the blue eyed damselfish is a great choice.

They have a rather peaceful temperament and can be kept in small schools of five or more individuals without issue, however, it is important to remember that they are still small fish and will not thrive if kept with large aggressive species such as lionfish.

Blue eyed damselfish typically grow to around four inches long at maturity.

This damselfish has blue eyes that are set against a light blue background. The blue eyes contrast nicely with the rest of its body, which is dark blue in color.

Origin and descriptions

blue eyed damselfish

The blue eyed damselfish is a species of fish found in the Indo-Pacific Ocean. They are typically bright blue with black markings on their dorsal fins and tails. These fish reach lengths of up to six inches and can be found near coral reefs and other sheltered habitats. They are generally peaceful, but they will protect their territory if threatened.

They are omnivorous and feed on a variety of small invertebrates, as well as algae. They are popular aquarium fish and can be easily bred in captivity. These fish make excellent pets for beginning aquarists.

Species profile

blue eyed damselfish

The blue eyed damselfish (plectroglyphidodon johnstonianus) is a species of fish in the family Pomacentridae. It is found in Australia, Fiji, and Indonesia.

They inhabit small coral reefs with clear water at depths between 0m to 15 m. Males are territorial during the breeding season which occurs from September through March making nests by cleaning out rock cavities or digging holes in the sand. The blue eyed damselfish can reach a size of up to 12 cm in length.

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The species is named for its bright blue eyes, which are used to communicate with other fish. They have a black body with a white stripe running along the dorsal fin and two other stripes on their pelvic fins. Juveniles are brown with light spots.

Scientific name

The scientific name of the blue eyed damselfish is Plectroglyphidodon johnstonianus.

Color and appearance

The blue eyed damselfish has a bright blue body with black markings on its fins. It is an attractive fish, and many people keep them in their aquariums for their beauty.

They are very active fish, and they need plenty of space to swim around. They are also social creatures, so it is best to keep them in groups of at least three.

They spend most of their time swimming near the surface, and they tend to be very peaceful fish that will not bother other tank inhabitants. They are also a small tropical reef-dwelling species with an eyespot on their dorsal fin which serves as camouflage in the coral reefs it inhabits. Overall, they are ideal for beginner saltwater aquarium hobbyists.

They grow to be around six inches long, and their lifespan in captivity is about five years depending on the environment they are kept in. They need plenty of places where they can hide; you should provide them with lots of rocks and crevices to create caves. Also include some open areas for them to swim in.

Range and habitat

The blue eyed damselfish is found in the tropical waters of the Atlantic, Pacific, and Indian oceans. They inhabit coral reefs where they feed on small invertebrates like crustaceans and worms.

They primarily feed on zooplankton and small invertebrates, like crustaceans. These include things such as shrimp larvae, brine shrimp, or even smaller fish that they can catch in their mouths! They also eat algae to supplement their diet with certain vitamins and minerals.

Their habitat must be at least 30 gallons for a single blue eyed damselfish, and they should have a tankmate of similar size. They are peaceful creatures but may be aggressive towards other fish if kept in too small of an environment.

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They love to live where there is plenty of vegetation for them to eat as well as open areas that allow them to swim around easily. With these things in mind, you can set up a nice habitat for them.


The blue eyed damselfish grows to about six inches in length

Tank size

Blue eyed damselfish are best kept in tanks that are at least 30 gallons, preferably larger. They should have a tankmate of similar size for their company.

It is important to provide them with plenty of places where they can hide so you should include rocks and crevices to create caves. Also provide some open areas for them to swim.

They love to live where there is plenty of vegetation for them to eat, as well as open areas that allow them to swim around easily. With these things in mind, you can set up a nice habitat for them.

Life cycle

The larval stage of blue-eyed damselfish typically lasts about 30 to 50 days. During this time, the larvae will drift and feed in open water before settling on a reef where they can find food near their own size. The larval stages are particularly important because it is during these early life phases that many fish species become adapted to their adult habitats.

Once they reach maturity, blue-eyed damselfish can live up to four years. In the wild, these fish typically grow to about two inches in length, but individuals in captivity have been known to reach six inches long. Theyare generally considered reef dwellers and can be found in the Indo-Pacific and Red Sea.

However, because they are so common and widespread in their habitats, blue-eyed damselfish have also become a popular fish for marine aquaria.

Are they aggressive or peaceful?

Blue eyed damselfish are generally considered to be a peaceful fish species. They typically only attack other fish when they feel threatened or when their territory is invaded. In fact, many aquarists consider them to be one of the best choices for a community aquarium because they get along well with other fish species.

Blue eyed damselfish care

blue eyed damselfish

Blue-eyed damselfish are relatively easy to care for and do not require a lot of special attention. In the wild, they typically live in areas with moderate water conditions and a pH level of around eight. They can tolerate a wide range of temperatures, from 68 degrees Fahrenheit to 86 degrees Fahrenheit.

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In the home aquarium, it is important to provide them with plenty of places to hide and swim. They also need a moderate level of water movement in the tank and should be fed a varied diet that includes both meaty and plant-based foods.

What they eat

Blue eyed damselfish are omnivores, which means they eat both plants and animals. Their diet consists of algae, invertebrates like worms and crustaceans, small fish eggs, planktonic organisms such as copepods (small crustacea), larvae from other species, diatoms on coral surfaces or sand grains.

Tank mates

They get along with a variety of other fish, but they should not be kept with aggressive or territorial fish. Some good tank mates include cardinalfish, clownfish, damselfish (other species), gobies, and blennies.

Some people like to keep blue eyed damselfish in groups, but others find them to be too aggressive with their own kind. If you want to keep them in groups, make sure that they are of different species and the same size so they don’t fight.

Water conditions

Blue eyed damselfish do not need specially difficult water conditions, but they will be most comfortable with a specific gravity of around one and a half ounces per gallon. The temperature should stay between 28°C and 31°C (82°F to 88°F) and the pH level should be kept between eight and nine. Salt content of at least five percent is also preferred.

Blue eyed damselfish will live in a tank with water conditions like these for their entire lives, but if you want them to breed, they should be kept in slightly different conditions, which is a 15°C lower temperature and a pH level of seven rather than eight or nine.


Blue eyed damselfish are one of the easiest fish to breed in captivity. The male will build a nest out of sand and coral rubble, and then court the female by swimming around her with his dorsal fin extended. If she is interested, she will follow him to the nest and they will spawn together.

The eggs will hatch in about two days, and the fry will be able to eat small invertebrates right away. They can be raised in a community tank with other fish of similar size, or you can set up a separate breeding tank for them.


The blue eyed damselfish has a lifespan of about eight years.

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Parasites and diseases

The blue eyed damselfish are affected by parasites and diseases such as:

  • The black spot disease, caused by the microsporidian “Dermocystidium Kawaguchi“. Symptoms include loss of coloration and appetite. This can be treated with antiprotozoal drugs like metronidazole or chloroquine.
  • The sea lice, caused by the copepod “Lepeophtheirus salmonis“. Symptoms include small white nodules on parts of the body and fins, high mortality rates in young fish, loss of appetite due to pressure damage around parasites. This can be treated with ponazuril at a concentration of 0.01%.
  • The flukes, caused by “Lethal red sacculitis” (trematode). Symptoms include loss of appetite and general weakness due to digestive tract damage. This can be treated with praziquantel at a concentration of 100 ppm for 48 hours; however, the fish’s environment must also be treated for the parasites.


The blue eyed damselfish are preyed on by a variety of predators, including:

  • The barracuda, which can easily outpace the fish and swallow it whole.
  • The moray eel, which coils around its prey before biting into it with sharp teeth.
  • Other predatory fish such as sharks and tuna.
  • Birds such as the brown noddy and red-tailed tropicbird, which prey on juvenile fish.

Does it make good pets?

The blue eyed damselfish is not a good choice as a pet because it requires expert care.

  • The temperature should be kept between 77 and 80 degrees Fahrenheit, with the pH around eight.
  • They prefer live food such as brine shrimp or bloodworms to flake foods.
  • It may damage aquarium plants due to aggression.
  • It can be difficult to breed in captivity.



The blue eyed damselfish is a beautiful fish that can be found in the coral reefs of the Indo-Pacific. It has a lifespan of about eight years and is preyed on by a variety of predators. It is a beautiful fish that makes an interesting addition to any saltwater aquarium. However, it requires careful care and should not be kept by novice aquarists. With the right conditions, it can live up to eight years.