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Pseudomugil gertrudae

The Blue-Eyed Wonders of Pseudomugil

The word Pseudomugil refers to a specific genus of small fish with blue-eyes found in New Guinea and Australia. Here they live in brackish water as well as freshwater streams and rivers. These fish tend to be slender with two dorsal fins and the most striking of blue eyes. There are a total of 15 species in the genus of Pseudomugil, some of which are more popular than others. These fish are entertaining and utterly stunning to observe and make an ideal breeding project.

Spotted Blue-Eye

The spotted blue-eye, or Pseudomugil gertrudae, is one of the most commonly mentioned species in this genus. This species was named after the wife of a German naturalist and is found in Trangan, part of the Aru Islands Group in eastern Indonesia. Most of the fish you will find in aquariums or for sale have been bred in captivity.

These fish prefer marginal zones with shallow waters, such as slow-moving, standing waters, or heavily vegetated areas of small streams, swamps, lakes, billabongs, and creeks. Within these areas, you will frequently find them in submerged woody features like roots or branches or among leaf litter. The ideal habitats for spotted blue-eyes will have surface vegetation, either growing or floating.

Pseudomugil gertrudae

When caring for a Pseudomugil gertrudae, you will want to get an aquarium with a base that is at least 45 x 30 centimeters as these fish can grow up to 30 to 38 millimeters long. This particular species is perfect for those who aquascape as they prefer tanks with dense plants. You can also add driftwood branches or roots or other floating branches to block out light and make the fish feel more comfortable. You will want to add moss as well if you plan on breeding the fish.

Opt for water that is well-oxygenated and has some flow. The pH of the water should be between 4.5 and 7.5 and it should have a hardness of between 90 and 215 ppm. The ideal temperature is 69.8 to 82.4 degrees Fahrenheit.

The spotted blue-eye will feed on suspended or floating invertebrates, phytoplankton, or zooplankton when in the wild. You should aim to feed a captive Pseudomugil gertrudae live foods like micro worms, Artemia nauplii, Moina, or Daphnia, but you can also give them some crushed floating dried food.

You will want to keep this particular species with only fish of the same variety or others of a similar size and behaviour pattern. These are timid animals which means they will be out competed for food. Because this group is considered a shoaling species, you want to have at least 8 to 10 of them in your group. This will make your display more natural and decrease their nervousness. Males are more colourful and patterned than females. This species scatters their eggs and females can release several eggs each day for a few days. If you have a large enough aquarium, some fry are likely to survive.

You might not find Pseudomugil gertrudae for sale in your local store but do ask the staff if they can keep a look out for you as they do crop up. Typically, they are not so colourful in their holding tanks which means they can often become overlooked…until they begin to develop their adult colours at which point they are snapped up promptly.

Forktail Blue-Eye

The forktail blue-eye, or Pseudomugil furcatus, is found in a similar area as the spotted blue-eye, but you will not find wild specimens available for your aquarium. You may also hear this species referred to as a yellow forktail or forktail rainbowfish. This particular species prefers streams with clear water, a current that is slow to moderate, and heavy vegetation. Forktail blue-eyes can grow to 40 to 60 mm long and their aquarium should be at least 60 x 30 cm.

You will want to keep your Pseudomugil furcatus in a tank with dense plants, as with the spotted blue-eye. They will also enjoy the same floating plants as the other species. Given the forktail blue-eye lives in an area with limited temperature variations, you will want to keep their tank between 75.2 and 82.4 degrees Fahrenheit. The pH should be between 7 and 8 and the water hardness should fall between 268 and 536 ppm.

The diet of the forktail blue-eye is nearly identical to that of the spotted blue-eye. As a shoaling species like the previous one, they should be in a group that has a minimum of 8 to 10 other fish. They can, however, do well in a community aquarium as long as you select the other species correctly. Choose ones with similar requirements, disposition, and size. Good ideas include smaller melanotaeniids, eleotrids, gobiids, or cyprinids. One of the best choices to share a tank would be Tateurndina ocellicauda, an eleotrid known as the peacock goby.

The breeding and mating patterns of the forktail blue-eye is very similar to that of the spotted blue-eye. This means that if you would like to breed them, you will either have to set up a large colony in an aquarium with enough hiding spots or keep the eggs separate from the adults after they are released. The colours displayed by males when breeding – especially when flaring their fins – is a sight to behold; it’s nothing short of a firework display.

Pacific Blue-Eye

The Pacific blue-eye, or Pseudomugil signifer, is considered to be the most widely-distributed of all Pseudomugil species within Australia.

The Pacific blue-eye is usually found within 15 to 20 kilometers of sea, but can have a range of habitats. These fish frequently live in coastal mangrove creeks, salt marshes, and swamps, but may also live in either pure freshwater environments or full marine conditions. You will typically want to keep these fish in an aquarium with a base of at least 60 x 30 centimeters. They may reach between 35 and 70 millimeters in length.

As with the other Pseudomugil species mentioned, you should set up the tank with plenty of vegetation, including floating driftwood and plants. Consider adding moss if you want to encourage breeding. This species does best in water with a pH of 6.5 to 7.5, a hardness of 90 to 268 ppm, and a temperature of 68 to 78.8 degrees Fahrenheit. They have the same diet as the other Pseudomugil species mentioned and should also be kept in groups of a similar size. If you have the larger varieties that are typically found in the north of Australia, make sure your tank is large enough if you have several mature males as they may become aggressive during spawning.


Thank you to the photographer of the image above for allowing its use under the creative commons licence https://commons.wikimedia.org/wiki/File:Pseudomugil_gertrudae_ARUII_Maennchen.jpg

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