Pajama Cardinalfish Overview, Care & Breeding Guide

If you are looking for a peaceful, easy-to-care-for fish for your saltwater tank, you should definitely consider pajama cardinalfish.

The vibrantly-colored fish have unique patterns and are fun to watch as they dart around the tank. In fact, if kept in groups, they add life to your aquarium. It is also an excellent beginner-friendly fish.

Excited to learn more about these small, cute finny buddies? Let’s dive right in.

What are the Characteristics of Pajama Cardinalfish?

OriginIndo-Pacific region: From Java to Fiji, From Ryukyu Islands to the Great Barrier Reef, Coral Sea, Japan, Korea, Hawaii, Tonga
Scientific NameSphaeramia nematoptera
Common NamesPyjama cardinalfish, Polka Dot cardinalfish, Spotted cardinalfish, Coral cardinalfish, Cardinalfish, PJ cardinalfish, Mangrove cardinalfish
IUCN Red List StatusLeast Concern
AppearanceGreenish-yellow face, large red or orange eyes, silver-based deep body, a bold black band from dorsal fin to behind the ventral fins. Red or orange polka dots on the rear side toward the tail. Two high-raised dorsal fins.
SizeUp to 8.5 cm (3.3 in)
LifespanIn the wild: 1 to 2 years. In captivity: up to 5 years.
TemperamentGenerally peaceful, territorial, aggression among males during breeding
Reef SafeYes, but not for all reef organisms
Tank LevelMiddle and bottom dwellers
Water Temperature72-80 °F (22-27 °C)
pH Level8-8.5
Water Hardness8-12 dKH
Care LevelEasy
Minimum Tank Size40 gallons for two. 125 gallons or more for a school
Tank EnvironmentTank with plenty of swimming space, hiding spots with rocky overhangs, caves, corals, plants and sea anemones.
DietCarnivore, micro predators
Tank MatesOwn school, calm and peaceful fish of similar size

What is the Natural Habitat of Pajama Cardinalfish?

The pajama cardinalfish lives in the Indo-Pacific region, from Java to Fiji, the Ryukyu Islands to the Great Barrier Reef, and even in the Coral Sea, Hawaii, and Tonga. It was initially found near Japan and Korea.

The fish prefers to dwell at depths of 1-14 meters (3-46 feet) in tropical waters. The nocturnal creatures, though mainly found in groups, sometimes appear in solitary pairs.

This species thrives in bays and lagoon areas with soft bottoms like mud or sand and occasionally roams near rubble from broken coral reefs.

It hides among specific coral branches like Porites nigrescens and P. cylindrica during the day. At night, it ventures out close to the ocean floor in search of small crustaceans.

These species have been assessed on the IUCN Red List of Threatened Species in 2021 and are categorized as having a Least Concern status, indicating a relatively stable population.

Which family does Pajama Cardinalfish belong?

The fish belongs to the Apogonidae family under the Kurtiformes order and is scientifically known as Sphaeramia nematoptera.

However, it is popular worldwide by a variety of names, like

  • Pyjama cardinalfish
  • Spotted cardinalfish
  • Polka Dot cardinalfish
  • Coral cardinalfish
  • Cardinalfish
  • Mangrove cardinalfish
  • Pj cardinalfish

Fun Fact: The pajama cardinalfish loves food. If you offer it treats throughout daylight hours, the nocturnal fish may become active during the day, i.e., diurnal.

How does Pajama Cardinalfish look?

Two spotted cardinalfish in a tank

If you’re interested in exploring the fish’s beauty, let’s delve into the specifics right away!

What is the Size of Pajama Cardinalfish?

The pajama cardinalfish is a small fish, growing up to 8.5 cm (3.3 in) long.

What is the Color of Pajama Cardinalfish?

The pajama cardinalfish is colorful with a greenish-yellow face and silver-based body marked by a bold black band from the dorsal fin to behind the ventral fins.

Its strikingly large red or orange eyes aid night vision. The posterior has red or orange polka dots toward the tail.

The pelvic fins are dark brown, the front dorsal fin is yellow, and the hind one is transparent. The pectoral, caudal, and anal fins are also transparent.

The juvenile fish has yellow heads that fade as it ages. This vibrant coloration resembling pajamas earned the fish its name.

The colors also help the fish stay hidden among sea urchins. The black band camouflages it within the spines, and the orange-dotted posterior blends seamlessly with the marine surroundings, making it almost invisible.

What are the Features of Pajama Cardinalfish?

The fish has a deep body 1.8-2 times its length. It features two distinct high-raised dorsal fins. The hind one is broader and transparent with a trailing filament, unlike the front one.

How can you differentiate between a male and a female Pajama Cardinalfish?

It’s challenging to distinguish male and female pajama cardinalfish.

Males are a bit larger, with longer secondary dorsal fins and an extended tip, while females have fuller bodies.

During breeding, males develop swollen jaws and carry the fertilized eggs for almost an entire month before they hatch.

The spawning female’s abdomens swell with eggs, making them distinguishable.

How does Pajama Cardinalfish behave in the aquarium?

The pajama cardinalfish is a social, peaceful fish that blends well in community saltwater tanks. The schooling species enjoys being with its own kind.

A school of this fish establishes strict hierarchies where the largest male takes control of the group but doesn’t use aggression.

It also establishes territories, often with specific hiding spots. It’s a slow and methodical swimmer and prefers staying in the middle of the tank.

The nocturnal fish is naturally quiet and shy, active at night, and rests in shaded areas during the day. It can be trained to become more diurnal.

Males might get aggressive during breeding and might have small disagreements like fin flicking and chasing, but these rarely cause injuries.

What is the Lifespan of Pajama Cardinalfish?

In the wild, the pajama cardinals typically survive for 1-2 years. However, in captivity, their lifespan extends, reaching up to 5 years.

However, in my experience, if you can upkeep the best tank conditions, you can sustain the fish for 8 years.

Did you know?

The genus name of the fish “Sphaeramia” has two ancient Greek words:

  • Sfaira (meaning ball) refers to the fish’s round shape
  • Aima (meaning shark) refers to the shark-like high first dorsal fin

How to take care of Pajama Cardinalfish?

Pajama cardinalfish breeding pair

If you’re eager to add this fish to your aquarium, let’s explore further the care requirements of this easy-to-manage fish.

What is the Tank Size for Pajama Cardinalfish?

For a comfortable living space, we recommend a minimum tank size of 30 gallons for one pajama cardinal. But this is a schooling fish, so 40 gallons for two works better.

If you plan to keep a larger group, a tank of 125 gallons or more would be suitable. These slow swimmers need ample space to thrive.

What is the Water Chemistry for Pajama Cardinalfish?

The fish is hardy and can be forgiving of less-than-perfect water parameters. But to sustain for the longest time possible, follow these water parameters (strictly).

  • pH Levels: 8-8.5
  • Water Temperature: 72-80 °F (22-27 °C)
  • Water Hardness: 8-12 dKH
  • Ammonia: 0 ppm
  • Nitrite: 0 ppm
  • Nitrate: 0 ppm
  • Synthetic Salt Level: 26-33 ppt
  • Specific Gravity:1.020-1.025

What is the Tank Environment for Pajama Cardinalfish?

Your next task is to provide the fish with a secure and content environment. Here’s your guide on how to achieve that!

What are the Substrate options for Pajama Cardinalfish?

The cardinalfish can thrive in various substrate options, including bare bottom, coral rubble, light sand, or even a deep sand bed.

Which Plants does Pajama Cardinalfish like?

The fish likes hiding in plants like seagrass, making it a perfect addition to your tank.

Which type of Lighting does Pajama Cardinalfish need?

Pajama cardinals, being nocturnal species, need low, gentle lighting. Avoid moderate or bright lights as they can harm them.

What type of Décor does Pajama Cardinalfish need?

Pajama cardinals thrive in aquariums with rocky overhangs, caves, corals, sea urchins, and sea anemones. The hiding spots provide comfort and security during the day.

What is the Filtration system that Pajama Cardinalfish needs?

To keep your pajama cardinalfish, you need a clean tank. Use a strong, high-quality water filter. Ensure good oxygenation and watch for excess food or debris.

What is the Water Flow Rate for Pajama Cardinalfish?

The pajama cardinalfish prefers gentle to moderate currents in the tank. Some recommend strong current, but the fish may get hurt from it. It especially chooses corners with calm water currents and rests there.

Are Pajama Cardinalfish Reef Safe?

Pajama Cardinalfish are considered safe for reef aquariums. They won’t harm your polyps, corals, and clams. However, they may eat polychaete worms, tiny fish, and crustaceans. Other reef animals are safe around them.

Fish Care Tip: These fish tend to jump, so it’s advisable to use a tank lid, especially when they are newly introduced.

What is the diet of Pajama Cardinalfish?

Pajama cardinals are micropredators with a carnivorous diet. In their natural habitat, they feed on animal plankton that float in the water column, larvae of fish, and young crustaceans.

They can be fed with live, freeze-dried, or frozen meaty marine protein, and you can supplement with flakes and pellets.

A balanced diet for these fish consists of:

  • Bloodworms
  • Blackworms
  • Feeder shrimps
  • Small feeder fish
  • Mysis shrimps
  • Brine shrimps
  • Daphnia
  • Cockle
  • Copepods
  • Krills
  • Clams
  • Brine shrimp eggs
  • Cyclops
  • Artemia
  • Squids
  • Algae sheets
  • Seaweed sticks

They enjoy chasing live food but are not picky eaters. But the same is not the case with wild-caught fish.

If your fish is the same, follow these steps:

  • Introduce both the live food and the preferred food.
  • Gradually decrease the live food amount and increase the new options.

If this does not work, try this:

  • Skip a meal – don’t worry, it won’t make your pet fall sick.
  • Offer only the preferred food for 2-3 days.
  • If they don’t eat, reintroduce the mix of live and preferred food again and try over.

It’s best to feed them at night when they are most active. Eventually, you can also train them to eat during the day.

When to feed Pajama Cardinalfish?

Feed small amounts 3 times per day, with one meal after sunset. These fish are ravenous eaters but slow swimmers. So, in a tank with faster fish, they might struggle to compete for food.

What are the Tank Mates for Pajama Cardinalfish?

For a happy and stress-free environment, it’s best to keep a group of at least 6 pajama cardinals. These timid fish thrive in the safety and companionship of a school, mirroring their natural habitat.

When kept together, they feel secure and content, promoting their overall well-being.

Once you’ve got a school of them, you can entertain the idea of a community tank.

These species are gentle and peaceful, making them great companions for other peaceful fish species of similar sizes in your aquarium. Introduce them to the tank at the same time to reduce aggression.

Compatible species include:

  • Pipefish
  • Filefish
  • Dwarf angelfish
  • Dragonets
  • Gobies
  • Reef safe wrasses
  • Damsels
  • Blenny fish
  • Royal grammas
  • Dartfish
  • Hawkfish
  • Firefish
  • Chromis

Quick Tip: If your pajama cardinal fish gets bullied by other fish, rearrange the tank decor and add more hiding spots like rocks and caves. Consider adding more pajama cardinals to create a larger, safer community and reduce stress.

Which Tank Mates to Avoid for Pajama Cardinalfish?

Certain tank mates should be avoided when keeping pajama cardinals due to their timid nature and specific behaviors:

Larger predatory fish: They may perceive pajama cardinals as prey and harm or even kill them.

Aggressive and boisterous fish: These species may intimidate pajama cardinals, causing them to hide out of stress.

Ornamental shrimp, small invertebrates, tiny fish: Pajama cardinals might see them as potential food, posing a threat to these creatures.

What are the Common Diseases for Pajama Cardinalfish?

While hardy, pajama cardinalfish aren’t immune to sickness. They can face common issues faced by saltwater fish, so regular care is essential.

Disease NameCausesSymptomsTreatment
DropsyBacterial infection due to poor water qualitySwollen or bloated fish, raised scales known as pinecone scalesImprove tank conditions by removing floating debris, perform a 25% water change, maintain cleanliness, and use over-the-counter medication if necessary
Hole in the Head (HITH)Hexamita parasite, weak immune system, poor water conditions, inadequate nutritionHoles in the fish’s headConsult a veterinarian for prescribed medication, address weakened immune system causes like poor water conditions or nutrition
Saltwater or Marine IchCryptocaryon irritans parasite, stress-induced weakened immune systemSmall white spots on the fish’s fins and bodyQuarantine the fish, use over-the-counter medication following instructions, identify and mitigate stress factors to prevent further infections
ColumnarisBacterial infectionGray/white patches, lethargy, appetite loss, fin frayingEnhance water quality, antibiotics, reduce stress
Fin RotBacterial infectionFraying/disintegration of fins, fin discoloration, lethargy, appetite lossEnhance water quality, get rid of objects that may physically injure fish, add antibiotics

Author’s Note: If they lose color, check if they’re getting bullied by their tank mates. If all seems fine there, make sure your tank is the right size for your fish buddies.

How to Breed Pajama Cardinalfish?

Breeding pajama cardinalfish in aquariums can be a rewarding experience for fish enthusiasts. These fish are relatively easy to breed, making them a popular choice among hobbyists.

What is the Tank Setup for Pajama Cardinalfish?

While some say pajama cardinalfish do not require a separate breeding tank, my suggestion is you must still keep it in a separate breeding tank. This will prevent the fish from getting stressed by other species.

Ensure it’s spacious enough to accommodate 4 to 6 fish. Maintain pH 6-8 and other water parameters must stay the same as the main tank.

Provide ample hiding places using plants, corals, live rock, and decorations to reduce stress and encourage breeding behavior.

How to Choose and Prepare the Breeding Group for Pajama Cardinalfish?

Choose the brightest and healthiest specimens of the lot. Feed them enough high-quality carnivorous feed for a few months to condition them to spawn.

To enhance breeding success, provide your fish with a varied diet, including live adult brine shrimp, frozen mysis shrimp, squid, and clam. This balanced nutrition boosts their fertility, leading to a higher number of healthy hatching larvae.

What is the Spawning Behavior of Pajama Cardinalfish?

Pajama cardinals are paternal mouthbrooders; the male carries the fertilized eggs in his mouth. The fish spawns during the evening hours, making it hard to spot the mating.

They exhibit aggression during spawning. The male protects the female during egg transfer, and the female guards the male afterward.

What is the Incubation Period for Pajama Cardinalfish eggs?

During the incubation period, the male stops accepting food. He occasionally adjusts his jaw position during the incubation period. Eggs occasionally slip out but are expertly gathered back by the male.

Larvae hatch between day seven and eight, swimming out of the male’s mouth. Fry are free-swimming immediately after hatching. They are about 3mm long and are released around the sea urchin spines.

When to separate Pajama Cardinalfish fry from the parents?

Separate the parent fish and the fry soon after their birth. Once started, spawning occurs every two to three weeks during the breeding season.

So, if you want to breed the group more, rehouse the fry in a different tank. Otherwise, move the parent group to the main tank and raise the fry in the breeding tank.

Fry Care & Development

Initially, it can be hard to feed the fry. They’ll only accept live plankton. Once they get used to that, feed newly hatched brine shrimp, rotifers, or amphipods.

Pajama cardinalfish fry are aggressive, and they chase the non-aggressive fry. Separate them to enhance survival rates.

The fry grow rapidly and are not as sensitive to water parameters as other marine fish fry.

Breeding Tip: On the first time breeding, male fish sometimes drop or swallow the eggs out of fear of being malnourished. In that case, don’t give up. The males learn after attempting breeding a few times.

How to Buy Pajama Cardinalfish?

When selecting fish at your local store, focus on these factors to ensure you pick the healthiest ones that have:

  • Clear, bright eyes as cloudy or white eyes indicate health issues.
  • Full, unbroken fins such as torn or frayed ones suggest previous injuries or diseases.
  • Naturally extended fins are not tightly clamped against the body.
  • Alert and freely swimming specimens as hiding or cowering is a sign of stress or illness.
  • Plump, well-rounded bodies, avoiding thin, malnourished, discolored, or wounded ones.
  • Vigorous eating habits which indicate their well-being.

Purchase from reputable and trusted sellers or stores known for their quality fish. Check reviews and testimonials to ensure the reliability of the source.

A word from FishInAquarium

Pajama cardinalfish are fascinating species and great for a midsize saltwater tank. The dashing-looking fish are a great addition to community reef tanks.

They are also pretty inexpensive, so even if you are running on a budget, you can easily get a handful of them!

I hope you found this article informative and inspiring. If you enjoyed it, please consider sharing it with fellow hobbyists and friends who might find it helpful.

Remember, if you have any questions or need further assistance, you can always reach out to us via email. Our team will be elated to support you.

Happy fishkeeping!

Minnie B Miller - Professional aquarist and owner of FishInAquarium

About Minnie B Miller

Minnie B. Miller, a professional aquarist and owner of FishInAquarium, has over 8 years of expertise in fish breeding and care, gained through her roles at AquaticTX and Sea Lion Landing. Having honed her skills with various aquatic species, she is dedicated to empowering fellow enthusiasts by sharing her knowledge and experience.