Information, Batfish, Saltwater fish, Species

Pajama Cardinalfish (Sphaeramia nematoptera)

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by Jason Matthews



The Pajama Cardinalfish is an enthralling species of fish that has become a popular pet fish. It’s no surprise that these fish have a cult following among fish enthusiasts, given their distinct appearance and gentle demeanor.

This article will delve into the fascinating world of the Pajama Cardinalfish, covering topics ranging from its origin to its behavior and dietary requirements. Whether a novice or an experienced fish owner, you will undoubtedly learn something new about this endearing species. Grab a cup of coffee and join us on an exciting journey of discovery into the world of the Pajama Cardinalfish.


Scientific Name: Sphaeramia nematoptera
Common Names: Pajama Cardinalfish
Life Expectancy: 5-8 years
Adult Size: Up to 3 inches


Quick Overview
OriginIndo-Pacific region
Care LevelEasy
Tank LevelMid-to-bottom
Minimum Tank Size20 gallons
Water pH8.1-8.4
Water Temperature72-78°F
Water Hardness8-12 dKH
Tank MatesPeaceful, compatible with a variety of other saltwater fish

Fun Fact Corner

The Pajama Cardinalfish is unique in that it can change color at night, becoming darker to blend in with the darkness and protect itself from potential predators. This adaptability is a fascinating feature of this species that distinguishes it from other types of fish. 


The Pajama Cardinalfish, scientifically known as Sphaeramia nemotoptera, hails from the tropical waters of the Indo-Pacific region, specifically from the areas surrounding the Philippines and Indonesia.

These fish inhabit shallow reef environments, often hiding in crevices or swimming amongst the coral formations. The Pajama Cardinalfish is a relatively new species to the aquarium trade, discovered in the early 1990s by marine biologists. 

Appearance & Size

The Pajama Cardinalfish is a truly captivating species with an eye-catching appearance. They are distinguished by their bright orange coloration, offset by striking black stripes running vertically down the body. The fish’s stripes give it a distinct “pajama” appearance, hence the common name.

The Pajama Cardinalfish has a distinctive and endearing appearance due to its striking coloration, relatively flat body shape, small mouth, and large eye.

It’s worth noting that these fish can change their color to adapt to their surroundings, so their appearance can vary slightly depending on their surroundings.

The Pajama Cardinalfish is a small species that grows about 3 to 4 inches long when fully grown. This makes them an ideal choice for those with smaller aquarium setups, as they only require a little space to thrive.


Like many other fish species, the Pajama Cardinalfish is not sexually dimorphic, which means that determining the gender of an individual fish simply by looking at it can be difficult. However, physical and behavioral differences between males and females can be used to distinguish them.

Female Pajama Cardinalfish, for example, are often larger than males and may have a slightly rounder belly when carrying eggs. Conversely, males may have a longer body shape and be more aggressive toward other males during the breeding season.


The Pajama Cardinalfish is known for its peaceful and social behavior, making it an ideal candidate for a community aquarium. These fish are typically shy and will spend most of their time hiding among the plants or decorations in the tank. However, they are not particularly territorial and will only show aggression toward other fish species if they are similar in size and appearance.

Pajama Cardinalfish are known for their intriguing and entertaining behavior and their peaceful nature. For example, they can “flash” or change color, which they use to communicate or blend in with their surroundings. They are also known for swimming in groups, which can add interest and activity to your aquarium.


When choosing tankmates for your Pajama Cardinalfish, it’s important to consider their peaceful and social nature. These fish do best in a community aquarium, surrounded by other friendly and non-aggressive species. 

Here are some good tankmates options:

  • Firefish (Nemateleotris magnifica): These are small, colorful, and peaceful fish that won’t bother the Pajama Cardinalfish. They tend to stay near the bottom or middle of the tank.
  • Clownfish (Amphiprion spp. and Premnas spp.): Clownfish are generally peaceful, especially when kept without an anemone. They can coexist well with Pajama Cardinalfish.
  • Royal Gramma (Gramma loreto): This is a brightly colored fish with a half purple and half yellow body. They are peaceful and tend to stick to their territory, making them a good match for the Pajama Cardinalfish.
  • Watchman Goby (Cryptocentrus cinctus): These gobies are bottom-dwellers and are known for their symbiotic relationship with pistol shrimp. They are peaceful and won’t bother other tankmates.
  • Banggai Cardinalfish (Pterapogon kauderni): Another species of cardinalfish, the Banggai is also peaceful and can coexist with the Pajama Cardinalfish. However, ensure the tank is spacious enough if you’re keeping multiple cardinalfish to prevent territorial disputes.

It’s important to note that Pajama Cardinalfish should not be kept with more prominent, aggressive species as they can become intimidated and stressed.

Tank conditions

When it comes to keeping Pajama Cardinalfish in an aquarium, it’s important to provide them with suitable tank conditions. These fish are native to the tropical waters of the Western Pacific Ocean, so it’s essential to recreate a similar environment in your aquarium.

Pajama Cardinalfish prefer temperatures ranging from 72°F to 82°F, with a pH of 8.0 to 8.4. They also like water with a moderate to high hardness, which can be achieved by adding aquarium-grade salt.

It is important to provide a stable and healthy environment for your Pajama Cardinalfish in terms of filtration and lighting. A high-quality filter, such as a power filter or canister filter, can aid in the preservation of water quality and stability. Additionally, moderate lighting in the tank is recommended to promote healthy plant growth and reduce stress levels in the fish.


Pajama Cardinalfish are omnivores and have a varied diet in the wild. They will accept a wide variety of foods in captivity, including both meaty and vegetable-based options. A well-balanced diet is essential for keeping these fish healthy and thriving in an aquarium.

To provide a well-rounded diet for your Pajama Cardinalfish, feeding a combination of dried, frozen, and live foods is recommended. 

Some good options include:

  • Dried pellets or flakes
  • Frozen brine shrimp, mysis shrimp, and krill
  • Live or frozen bloodworms and blackworms
  • Vegetable-based foods such as spirulina or blanched spinach

It’s important to remember to feed your Pajama Cardinalfish appropriately, as uneaten food can quickly pollute the aquarium water. Providing 2-3 small portions daily is recommended, rather than a large feeding once daily.


Breeding Pajama Cardinalfish in captivity can be a challenging task, but it can also be a rewarding experience for the dedicated fish keeper. These fish have specific requirements for breeding, including proper water conditions, suitable tank mates, and a healthy diet.

A dedicated breeding tank with conditions similar to their natural habitat should be set up to breed Pajama Cardinalfish successfully. A water temperature of 77°F to 82°F, a pH of 8.1-8.4, and a specific gravity of 1.020-1.025 are required.

Furthermore, providing plenty of hiding places and cover in the form of live plants, caves, or other structures will aid in the creation of a suitable breeding environment for these fish. A breeding pair of Pajama Cardinalfish should also be carefully chosen, as compatibility and health are required for successful breeding.

Once the breeding environment has been established, it is important to encourage the Pajama Cardinalfish to spawn by providing a varied diet and maintaining proper water conditions. If the conditions are favorable, the female will lay her eggs in a safe place, usually near some cover, and the male will fertilize them.


The disease is a common concern for all fish owners, including Pajama Cardinalfish. Ich, Fin Rot, and Marine Velvet are the most common conditions affecting these fish.

Ich, also known as White Spot Disease, is a common parasite that causes white spots on the body and fins of fish. Poor water quality or stressful conditions typically cause this disease, and it is treatable with a combination of water changes, medication, and proper tank maintenance.

Fin Rot is another common fish disease that causes the fins to fray and disintegrate. This disease is frequently caused by poor water quality or aggressive tank mates, and it is treatable with proper water maintenance, medication, and stress reduction for the affected fish.

Marine Velvet is a parasitic infection that causes fish to be covered in a fine, golden-brown dust-like substance. This disease is frequently transmitted through the water and can be treated with proper water maintenance, medication, and stress reduction for the affected fish.

Maintaining good water quality, providing a healthy diet, and keeping the tank free of overcrowding and stress are all essential steps in preventing diseases in Pajama Cardinalfish. If you suspect your Pajama Cardinalfish is infected with a disease, seek professional advice immediately and treat it to prevent it from spreading to other fish.


Jason Matthews

My name is Jason Matthews, and welcome to my website. When other kids were bragging about how their dog could sit and roll over, I was bragging about my latest Betta Fish and the cool sea castle I just added to his aquarium. 

Jason aquariume

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