Pseudomugil signifer (Pacific Blue Eye Fish)

Pseudomugil signifer

Last updated on August 10th, 2022 at 05:16 pm

Pseudomugil signifer, also known as the Pacific blue eye fish, is one of many freshwater fishes found in Australia, and unlike some others in its family, it’s not endangered or threatened at all. Found in northern Australia from the coastal lowlands to the mountains surrounding rivers and streams, the Pacific blue eye fish may be rare in some areas but can be easily found elsewhere.

Pseudomugil signifer is a tropical freshwater fish found in the coastal rivers and streams of Australia, where it prefers water with rocky or sandy substrates and low current, or pools and backwaters of larger rivers. This species grows to an adult length of 6–9 cm and can be differentiated from similar Pseudomugil species by the fact that its abdomen has vertical barring that extends onto the tail fin.

Origin and descriptions

Pseudomugil signifer is a freshwater fish found in New Guinea. This fish has been introduced to other areas but has not been studied for impacts on indigenous populations of fish. In one area of Queensland, Pseudomugil signifer has out-competed three native species and reduced populations by 90 percent or more.

This phenomenon can be attributed to Pseudomugil signifer’s ability to survive in polluted conditions better than local species. While scientists are still working to understand how these changes will affect ecosystems, it is clear that invasive species can have significant negative effects on native plants and animals.

For example, American bullfrogs have invaded multiple regions of Australia and competed with native frogs for food. The impact of invasive species cannot always be predicted, so it is important to monitor and control new introductions before they become established.

Species profile

Pseudomugil signifer

Pseudomugil signifier belong to the family Pseudomugilidae. The common name for these fish is Pacific blue eye. They are native to Australia and New Guinea, where they inhabit streams and rivers in tropical rainforests. This species was first described by German naturalist Eduard Rüppell in 1837. The pacific blue eye is a small fish, reaching a maximum length of 9 centimeters (3.5 inches). The body is transparent with yellowish-orange fins and bright blue eyes. Juveniles have vertical stripes that fade as they mature.

Poecilia velifera (Giant Sailfin Molly)

The diet of Pseudomugil signifer consists primarily of insects, but may also include worms and insect larvae. These fish are carnivorous; they hunt their prey using sight and smell rather than using suction feeding or filter-feeding like other members of their order, Cyclopoida.

When hunting, these fish will dart towards their prey at high speeds; if successful in catching it, they will consume it on-site before moving on to find more food.

Common name

The common name of Pseudomugil signifier are Pacific blue eye fish, forktail rainbow fish, or just blue eyes fish.


The Pacific blue-eye is freshwater or brackish water fish of streams and ponds. It prefers shaded areas with lots of vegetation because it likes to hide out under leaves while waiting for food to swim by. It’s found in western New Guinea, Papua New Guinea, Indonesia, Solomon Islands, and northern Australia. They are not native to Hawaii or Guam. They prefer water that has a pH level between 6.5 and 7.5, which is neutral to slightly acidic water.

Pseudomugil signifier size

Male Pseudomugil signifier can grow up to 3.5 inches (9 cm) while females can grow up to 2.56 inches (6.5 cm) in total length.

Tank size

Pseudomugil signifer

The minimum recommended tank size for this species of fish is 10 gallons (76 liters).

Tank requirements

The Pacific blue eye fish needs to be kept in a species-only tank. The other species of blue eyes, Pseudomugil furcatus, can look almost identical and is aggressive to other pacific blue eyes. This could result in fighting and stress for your new addition to your tank.

A minimum of 10 gallons per fish should be provided. A 20 gallon or larger tank would work best if you plan on keeping more than one specimen. They are schooling fish so they will need at least 3 or 4 specimens to feel comfortable. They prefer water that is between 74-78 degrees Fahrenheit, but they will tolerate temperatures as low as 65 degrees Fahrenheit.

Wrestling Halfbeak Fish (Dermogenys pusilla)

They require a pH of 6.5-7.5 and have moderately hard water requirements. There is some debate about whether these fish are truly reef safe, however, there have been no reported cases of them eating corals or crustaceans in captivity so far (at least not yet).

They may eat small shrimp though, so caution should still be used when adding them to an established tank with shrimp present.

Tank mates

Pacific blue eyes are very peaceful fish, so you can keep them with many different species of fish. However, they do not do well with other pacific blue eyes. They should be kept in groups of 3 or more for best results.

This is because these fish are a schooling species. They need to have others around them to feel secure and display their beautiful colors to their full potential. When kept alone or in small numbers, these fish tend to be darker in color and withdrawn from human interaction.

Some good tank mates are other peaceful species of fish such as: danios, tetras, dwarf cichlids, catfish, and loaches. You should avoid keeping them with aggressive or territorial fish.


Pseudomugil signifer

Pseudomugil signifer live and breed in freshwater streams of Queensland, Australia. These fish are very peaceful and will rarely bother any other fish species in their ecosystem. In fact, they require isolation from other fish species to ensure that they will mate with one another!

This is because Pseudomugil signifer are sexually aggressive toward other male Pseudomugil signifers, but not toward female Pseudomugil signifers. If you have a pair of these fish in your tank, it’s best to isolate them before the breeding season begins so that they don’t fight each other.

If you do have a pair and want to get them to spawn, then you can add some salt into your tank for about two weeks before beginning a spawning cycle. Once you begin adding salt into your tank, make sure that you keep it at 1/3 salinity until after spawning has occurred.

Then, you can slowly decrease salinity levels over time as needed. It’s also important to note that when Pseudomugil signifer spawn, they release both eggs and sperm into the water column. The eggs float up toward the surface while males aggressively pursue females by nudging them until they release their eggs.

African Monodactylus Sebae (African moony)

It may take several days for all of your fish to spawn, so be patient! You should also watch out for fungus growing on your eggs, this means that they are no longer viable and should be removed. Now, once you have successfully hatched out baby fish, you need to feed them appropriately until they reach maturity.

To feed baby Pseudomugil signifer properly, provide them with plenty of small crustaceans such as mosquito larvae or Daphnia; if these aren’t available in your area, then brine shrimp nauplii work well too!

Are they aggressive or peaceful?

The Pacific blue eye fish is described as a peaceful community fish. They do best in groups of six or more. Keep tank mates to a minimum and observe their behavior before adding new members to their schools.

A good indicator of stress is when they are schooling together at dusk, but split up during daylight hours. It’s not an entirely natural lifestyle for them, so it may be time to replace some schoolmates.

Pseudomugil signifier care

Pseudomugil signifer

Pseudomugil signifer is a freshwater fish that can be kept in aquariums. They are best kept in groups of at least five. It’s suggested that groups should be separated by gender, as males can get aggressive with one another. In addition to having other pacific blue eye fish in their tank, they also need live plants and driftwood to keep them happy.

They prefer tanks with soft water and require high oxygen levels. This means they do not do well in tanks without filters or aeration. The ideal temperature for pseudomugil signifer is between 72-82 degrees Fahrenheit. When keeping pseudomugil signifer, it’s important to avoid copper-based medications because copper can cause permanent liver damage and even death in some cases.

Pseudomugil signifer diet

They are omnivores and will eat flake food, frozen brine shrimp, freeze-dried bloodworms, and tubifex worms. The only time you should give them live foods is when breeding.

Arnoldichthys Spilopterus (African Red Eyed Tetra)


This species can live up to 3 years in captivity.

Parasites and diseases

If you’re a beginner aquarist, you may have to deal with parasites and diseases that can invade your aquarium. That said, there are a few things you can do to reduce your risk of unwanted visitors.

Firstly, quarantine all new fish for at least two weeks before introducing them into your main tank. Secondly, remove any dead fish from your tank immediately—this will cut down on foul odors that attract disease-carrying organisms.

Finally, practice proper maintenance. Feed your fish just enough food so they don’t go hungry; change out about 10 percent of their water every week; clean their tanks regularly, and perform regular water changes.


Pacific blue eye fish often fall prey to larger predators as bycatch. Their colors allow them to blend in with their surroundings as a protective measure against large predators. They are able to survive despite these threats because of their high reproduction rate and fast growth rate in young fish. They can be eaten by sharks and groupers.

Do Pseudomugil signifer make good pets?

If you’re considering owning a pet fish, then you may want to consider buying Pacific blue eye fish. Although they don’t get pretty big, and grow up to 3.5 inches in length, they are still considered one of the best first aquarium pets.

Because these fish prefer cooler water temperatures, it’s best to keep them away from tropical areas with higher temps. They also prefer more subdued lighting conditions. However, if you can provide for their needs, then there is no reason why these fish can’t make great pets!