Pajama cardinal Best Guide 101: Appearance, Diet & All |2024

By: Martin McAdam
Updated: February 28, 2023

The Pajama Cardinal, also known as the Cardinalfish, is a popular tropical fish in the aquarium trade. It is a peaceful fish that is perfect for beginners. You can go with a pair, a group, or a single fish. They do best in an aquarium with plenty of hiding places and live plants. They are found in the Western Pacific Ocean.

These fish are ideal for a nano aquarium. They are among the few Cardinalfish that can be kept in a community tank. However, you must be mindful of their diet since they are prone to getting ich.

Pajama Cardinalfish care is not complex, but there are a few things you need to know before getting started.

This article will cover everything you need about Pajama Cardinalfish care, including tank size, diet, lifespan, and more!

So let’s get started with learning about their care!

Species Summary

Scientific name: Sphaeramia nematoptera
Common names:Pajama Cardinal, Cardinalfish
Family: Apogonidae
Origin: Western Pacific Ocean
Life expectancy: 5 years
Size: 3 inches (7.5 cm)
Minimum tank size: 20 gallons
Water temperature: 72°-79° F (22-26 C)
Specific gravity: 1.023 – 1.025
Diet: Carnivore, frozen, live
pH range: 8.1-8.4
Water hardness: 8-12 dKH
Water Type: Marine
Care level: Easy
Tankmates: Small peaceful fish, shrimp
Temperament: Peaceful

Pajama Cardinals, the scientific name Sphaeramia nematoptera, are a small, peaceful Cardinalfish species widespread in the aquarium trade. They are native to the Western Pacific Ocean and live among the reefs in the region. Not listed as an endangered or vulnerable species, they are easy to find and purchase.

In the wild, the group around the rocky areas of the reef hunted in the crevices. They are best kept in an aquarium with plenty of hiding places and live plants to make them comfortable in captivity. They can be kept in a community tank, but care must be taken to ensure that other species do not crowd them and that their diet is varied and nutritious.

The easiest way to distinguish between the males and females of a Pajama Cardinalfish species is by looking at their dorsal fin. This fin is long and flowing in males but will be more triangular in females.

Pajama Cardinal Appearance

One of the reasons that Pajama Cardinals are so popular in the aquarium trade is their unique appearance. They have a reddish-orange body with large black spots. Their bodies are silver but with irregular black spots on them. They also have long, flowing dorsal fins often tipped with yellow or white.

Pajama Cardinal Appearance

As a popular aquarium fish, several different color variants and morphs are available to aquarists. For example, you can find specimens with bluish tails or red fins and albino variants.

Their fins are long and flowing, with a yellow or white tip. These fish also have a large “pajama” pattern on their abdomen that looks like a long-sleeved shirt.

Pajama Cardinal Size & Growth Rate

Pajama Cardinals are a small fish species, only growing about 3 inches (7.5 cm) in length. Their growth rate is considered to be slow, but they can live for up to 5 years with proper care.

However, some environmental factors can significantly impact their growth rate and lifespan. Water temperature, diet, and a lack of hiding places can reduce their lifespan in captivity.

Pajama Cardinal Lifespan

The lifespan of a Pajama Cardinal is about 5 years. However, it is common for them to only live for 3-4 years in captivity. Environmental factors like water temperature and diet can significantly impact their lifespan.

As with most fish species, there is no guaranteed way to predict a Pajama Cardinal’s lifespan accurately. However, they can live in an aquarium environment for several years with proper care and attention.

Pajama Cardinal Breeding

They are relatively easy to breed if their water conditions are optimal. To breed them, you must first set up a separate tank that has been cycled and established with safe, healthy water conditions.

When choosing a breeding pair, it is essential to select fish that are healthy and of similar size. Once you have chosen a pair of fish, you can introduce them to their breeding tank. It is best to do this at night, as Pajama Cardinals are nocturnal creatures.

Pajama Cardinal Breeding

Once the fish have been introduced to their breeding tank, they will likely begin to spawn within 24 hours. After spawning, remove the eggs from the tank or leave them until they hatch. However, if left in the tank, keeping an eye on the brood and removing any that do not survive is essential.

Once your fry has hatched and grown, you may need to separate them into their tanks to ensure enough room and food.

By taking the time to carefully choose your breeding pair, establish safe water conditions, and monitor the fry once they have hatched, you can help to ensure that your Pajama Cardinal has a successful breeding experience.​

Pajama Cardinal Behavior & Temperament

These fish are fun to watch as they go about their day-to-day activities. Pajama Cardinals are generally peaceful fish, although they can be territorial with other members of their species. They should not be kept with much larger fish than them, as they may become intimidated and stressed.

However, the males can be pretty aggressive toward each other, so you should keep only one male per tank to reduce aggression. 

They have hierarchical social structures, with females at the bottom of the totem pole. The aggression is directed towards other members of their species and not towards other tank mates. 

They are hardy fish species and can adapt to various water conditions. However, ensuring that the water in your tank is always clean and well-oxygenated is essential.

To keep your Pajama Cardinal happy and healthy, provide them with a clean tank, plenty of space to swim and explore, and regular feedings of nutritious foods. With proper care, you can help your fish thrive for many years!​

Pajama Cardinal Care

They are rugged, hardy fish that are easy to care for. They are a peaceful species that can be kept in a community aquarium or a nano aquarium. They prefer hiding places like caves or rock formations and love live plants.

In addition to providing hiding places, it is essential that you also pay close attention to their diet. These fish are carnivorous and will eat all kinds of meaty foods. They prefer frozen meaty foods over live ones, but either will work.

Pajama Cardinal Care

Overall, they are an excellent choice for hobbyists looking for an easy-to-care-for fish that looks great in their aquarium. With a proper diet and plenty of hiding places, they can stay healthy and live longer even as they grow to full size.

Here are some tips for keeping a Pajama Cardinal in your home aquarium:

Pajama Cardinal Tank Size

PajThe minimum tank size for this species is 20 gallons (75.7 L). But, if you plan on keeping more than one fish, it is best to get a larger tank.

Add plenty of hiding places and live plants when setting up your tank. These fish love spending their time in caves and under rocks, so you must provide them with plenty of these hiding spots.

Pajama Cardinal Water Parameters

Pajama Cardinals are hardy fish that can adapt to various water parameters. However, they prefer water that is on the alkaline side with a pH of 8.1-8.5. They also prefer soft to medium water in hardness, with a dGH of 8-12.

As for temperature, these fish do best in water between 72°-79° F.

However, keeping fish healthy ensures their water is clean and well-filtered. This means performing regular water changes and using a high-quality filter.


When it comes to filtration, you have a few different options. But you must choose a filter that is appropriate for the size of your tank.

For example, if you have a 20-gallon (75.7 L) tank, you will need a filter that can handle at least 100 gallons per hour (380 L/hour).

Some recommended filters for Pajama Cardinals include:

  • Canister Filters: These filters are potent and effective but require more maintenance than other options.
  • Power Filters: These filters are great for smaller tanks as they do not take up a lot of space. They can also be easy to clean and maintain.
  • Hang-On-Back (HOB) Filters: For those who do not want to deal with the hassle of a canister filter, HOB filters are a great option. They are easy to set up and maintain and provide plenty of filtration for your tank.


As mentioned, Pajama Cardinals prefer water that is between 72°-79° F.

You must invest in a heater to keep your tank at this temperature.

There are different kinds of heaters available, such as:

  • Submersible Heaters: These heaters get submerged directly into your tank and are easy to install.
  • Thermostatic Heaters: These heaters come with an integrated thermostat, which makes them especially effective at maintaining the correct temperature in your aquarium.

Whether you choose a submersible or thermostatic heater, you must monitor the temperature of your tank closely and make sure that it stays between 72-76 degrees Fahrenheit (22-24 degrees Celsius).


Pajama Cardinals are not particularly fussy fish when it comes to plants. They will do well in both live and artificial plants.

Some recommended plant options for your tank include:

  • Java Fern: This plant is an excellent choice for beginner aquarium hobbyists as it is relatively easy to care for. It can also help to keep your tank clean and free of algae.
  • Anubias: This plant is another good option for beginner aquarium hobbyists. It is hardy and can tolerate a wide range of conditions.
  • Amazon Sword: This plant is a bit more challenging to care for than the other two options, but it does provide a beautiful and natural-looking focal point for your tank.


Pajama Cardinals do not have any special requirements when it comes to lighting. They can do well in both low and high light conditions.

Some recommended lighting options for your tank include:

  • Fluorescent Lighting: This type of lighting is inexpensive and easy to find. It is also perfect for planted tanks, providing the right light for plants to thrive.
  • LED Lighting: This type is more expensive but provides bright and vibrant colors in your aquarium. If you have live plants, LED lighting may be a better choice than fluorescent as it can provide the light they need to grow.

Ultimately, the type of lighting that you choose is up to you. Ensure you do not leave your lights on for more than 12 hours daily, which can cause algae to grow in your tank.

Co2 Systems

Adding a CO2 system can be beneficial if you keep live plants in your tank. A CO2 system helps to maintain plant growth by providing the plants with nutrients and carbon dioxide.

While this system is not required for Pajama Cardinals, it can help keep your aquarium looking beautiful and healthy. Many types of CO2 systems are available, so it is essential to research and find the one that is right for you.

Some recommended CO2 system choices include:

  • Pressurized CO2 Systems: These systems are the most effective and reliable choice for aquarium hobbyists who want to grow healthy, vibrant plants. However, they can be more expensive and require additional maintenance than other options.
  • Non-Pressurized CO2 Systems: This type of system is less expensive than pressurized CO2 systems but also less effective. Non-pressurized systems can be a good choice for beginner aquarium hobbyists just starting with live plants.
  • DIY CO2 Systems: If you are on a budget or are simply interested in trying your hand at DIY projects, creating your CO2 system is an option. Many online tutorials help you create a cost-effective and affordable system.

Water Conditioners

While Pajama Cardinals are relatively hardy fish, it is still important to invest in water conditioners to help ensure that they stay healthy and happy.

Some recommended water conditioner options include:

  • Stress Coat: This type of water conditioner helps your fish recover from stress caused by transport or changing water conditions.
  • Aquarium Salt: Using aquarium salt in your tank can benefit fish and plants as it helps maintain an optimal pH balance. It is also relatively inexpensive and easy to find at most pet stores or online retailers.


Pajama Cardinals do not require any particular substrate, but adding some to your tank can make your aquarium look more natural and appealing.

Some recommended substrate options include:

  • Gravel: This is probably the most common type of substrate used in fish tanks. It provides a safe, natural-looking environment for your fish to swim in.
  • Sand: This type of substrate is becoming increasingly popular among aquarium hobbyists. It can provide a more natural look for your tank and is easier to clean than gravel.
  • Coconut Fiber: This type of substrate is perfect for planted tanks as it helps to maintain the optimal pH level for live plants to thrive.

As many different substrate types are available, it is essential to research the one that is right for you and your Pajama Cardinalfish.​


In addition to choosing the proper lighting, substrate, and water conditioners for your Pajama Cardinal tank, adding some decorations is essential.

Some recommended decoration options include:

  • PVC Pipe: This decoration can be used as a hiding place to add visual variety to your tank.
  • Driftwood: This is a popular choice for aquarium hobbyists who want to create a natural-looking environment for their fish. It can also provide valuable hiding places for your fish.

When choosing decorations for your Pajama Cardinal tank, it is essential to remember that they should be safe for fish and plants. Additionally, it is always good to research and finds the decorations that best suit your particular tank setup and needs.​

Other Tank Accessories

You must purchase a few other things to set up your Pajama Cardinal tank.

Some of the most important things to remember are:

  • Aquarium Thermometer: An aquarium thermometer is a helpful tool that allows you to monitor the water temperature in your tank quickly.
  • Air Pump: An air pump is essential to any aquarium setup. It helps keep toxic gases from building up in your tank and provides steady air to all the plants and fish that call your aquarium home.
  • pH Meter: A pH meter is a valuable tool that allows you to monitor and maintain the optimal pH levels in your tank.

With the proper lighting, substrate, water conditioners, and decorations, you can create a healthy and beautiful habitat for your Pajama Cardinalfish. By researching and carefully considering your options, you can help your fish live a long and happy life in the comfort of their own home.​

Water Changes

Pajama Cardinals are relatively hardy fish but require regular water changes to stay healthy and happy. Changing at least 20% of the water in your tank each week is generally recommended.

Water changes are essential because they help remove toxins and waste from your aquarium. They also help to keep the water quality high, which is essential for the health of your fish.

When changing the water in your tank, using a water conditioner designed to remove chlorine and other harmful chemicals from tap water is essential. It is also a good idea to slowly acclimate your fish to the new water by adding a small amount and then waiting for several minutes before slowly adding more.

By performing regular water changes and taking the necessary steps to keep your Pajama Cardinal’s tank clean and healthy, you can help to ensure that your fish live long and happy lives.​

Cleaning The Tank

In addition to performing regular water changes, cleaning your Pajama Cardinal’s tank is also essential.

The frequency with which you need to clean your tank will depend on several factors, such as the size of your tank, the number of fish you have, and the type of filtration you use.

Regardless of how often you need to clean your tank, it is essential to take the following steps:

  • Remove all the fish from their tank and place them in a temporary holding tank or another aquarium while cleaning.
  • If necessary, use a vacuum to remove any debris from the gravel.
  • Remove any decorations that need to be cleaned and scrub them with a soft brush.
  • Use an aquarium-safe cleaner to clean the inside of the tank, being sure to avoid any areas where your fish will be swimming.
  • Once the tank is clean, you can put the fish back in and add any new decorations or plants that you may have.

Regularly cleaning your Pajama Cardinal’s tank can help keep their home clean and healthy, ultimately leading to happier and healthier fish.​

Cleaning The Filter

It would be best if you also took the time to clean your Pajama Cardinal filter regularly. This is important because it will help to ensure that your tank stays healthy and free of toxins.

There are a few different methods for cleaning your filter, depending on the type that you are using. Some filters can be rinsed or replaced with new filter media, while others must be taken apart and cleaned with a particular filter-cleaning solution.

Regardless of your method, it is essential to clean your filter regularly to ensure optimal water quality and keep your fish healthy and happy.​

Testing The Water

In addition to regular cleaning and maintaining your Pajama Cardinal’s tank, it is also a good idea to test the water regularly.

Many different aquarium testing kits are available, so you can choose the one that best suits your needs and budget. Some basic tests will include measuring your water’s pH, temperature, and ammonia levels.

Regularly testing the water in your tank will help you ensure it is always safe and healthy for your fish. Keeping your aquarium clean and well-maintained can help ensure your Pajama Cardinal lives long and happy.

Pajama Cardinal Common Possible Diseases

Although Pajama Cardinals are generally healthy fish, there are a few diseases that they are susceptible to.

Some of the most common include:

  • Hexamita: This parasitic infection can cause lethargy, loss of appetite, and intestinal damage.
  • Columnaris: This bacterial infection can cause fins to rot and ulcers to form on the skin.
  • Ich: This is a parasitic infection that can cause white spots to form on the fish’s body.
  • Velvet: This parasitic infection can cause your fish to develop a yellow or gold coating.

If you notice any of these symptoms in your Pajama Cardinal, taking them to the vet as soon as possible is essential for proper treatment. By being aware of common diseases affecting Pajama Cardinals and taking steps to prevent and treat them, you can help ensure your fish stay healthy and happy.​

Pajama Cardinal Preventing Diseases

There are a few things that you can do to help prevent diseases in your Pajama Cardinal. First, it is essential to purchasing your fish from a reputable dealer. This will help ensure they are healthy and free of parasites or diseases.

It is also good to quarantine new fish before adding them to your tank. This will help prevent the spread of any diseases they may carry.

Finally, you should regularly clean and maintain your tank. This will help to keep the water quality high and reduce the risk of your fish becoming sick.​

Their care can seem like a lot of work, but it is simple. Cleaning and maintaining your tank can help ensure your fish are always happy and healthy. Regular water tests and tank cleanings will go a long way in preventing diseases, and quarantining new fish will help keep your tank free of parasites or illnesses. You can ensure that your Pajama Cardinal lives a long and happy life with a bit of care.​

Pajama Cardinal Treatment And Medications Of Diseases

If your Pajama Cardinal becomes sick, a few treatment options are available. First and foremost, it is essential to seek the help of a qualified veterinarian who is experienced in treating fish.

Many different medications and treatments can be used to treat common diseases like Hexamita, Columnaris, Ich, and velvet. Some of the most common medications include:

  • Antibiotics: These are used to treat bacterial infections.
  • Antifungals: These are used to treat fungal infections.
  • Parasiticides: These are used to treat parasitic infections.

Depending on the severity of the disease, your vet may recommend a course of treatment that includes one or more of these medications. It is essential to follow their instructions carefully to ensure your fish recover quickly and safely.

In addition to medications, there are a few things that you can do at home to help treat your Pajama Cardinal. First, it is essential to raise the water temperature in your tank. This will help to kill any parasites or bacteria that are present.

You can also add a few aquarium salt drops to the water. This will help to relieve any discomfort or inflammation and promote healing.

Over time, these simple at-home treatments combined with medication should help your Pajama Cardinal recover quickly from diseases. You can help your fish return to health and happiness with proper care and medical treatment.​

Pajama Cardinal Food & Diet

They are micro predators who need meaty foods to survive. They typically eat small crustaceans, worms, and insects in the wild. 

In captivity, they can be fed a variety of foods, including:

  • Bloodworms
  • Brine shrimp
  • Daphnia
  • Mysis shrimp
  • Chopped squid

Feeding your Pajama Cardinal various foods is essential to ensure they get all the necessary nutrients. A too-limited diet can lead to health problems down the road.

You should also feed your small fish meals several times a day. This will help them better digest their food and reduce the risk of becoming sick.

By providing them with a variety of nutritious foods, you can help them to stay happy and healthy. A healthy diet is essential for keeping your fish happy and disease-free.​

Pajama Cardinal Diet Foods To Avoid

There are some foods that you should avoid feeding your Pajama Cardinal. These include:

  • Highly processed or frozen foods: Processed and frozen foods can have high levels of preservatives, which can lead to health problems in the long term.
  • Starchy items: Starchy items, such as bread and pasta, can quickly break down into sugar, leading to health problems in fish.

Avoiding these foods can help ensure your Pajama Cardinal stays healthy and happy.

Pajama Cardinal Feeding Schedule

In general, they need to be fed at least once per day. However, the frequency and amount of food you feed your fish will depend mainly on their size, age, and health status.

If you are unsure how much to feed your Pajama Cardinal, consult a qualified aquarium specialist or veterinarian. Generally, starting with a small amount of food is best, and gradually increasing it as needed.

Some simple guidelines to follow when feeding your Pajama Cardinal include:

  • Feed your fish various foods, including pellets, flakes, live, and frozen food. This will ensure that they are getting all the nutrients they need.
  • Avoid feeding your starchy fish items, such as bread and pasta, as these can quickly break into sugar.
  • Feed your small fish amounts of food several times per day rather than one large meal. This will help ensure they get the necessary nutrients without over-stuffing their stomachs.

Overall, providing a nutritious and well-balanced diet for your Pajama Cardinal is essential for keeping them healthy and happy. Proper care can help your fish stay solid and healthy for many years.​

Pajama Cardinal Tank Mates

When choosing tank mates for your Pajama Cardinal, it is essential to be mindful of their size, temperament, and behavior. Generally speaking, these fish are peaceful and do well when kept with other small tropical community species. Some good options to consider include the following:

Monitoring their aggression levels is essential to keep more than one Pajama Cardinal in your tank. While these fish are generally peaceful with other species, they can be very territorial and aggressive regarding their kind.

Keeping only one male per tank is best if you are concerned about aggression levels. This will help to reduce the likelihood of aggression and fighting.

Fish To Avoid

  • Large fish species may see the Pajama Cardinal as prey
  • Other aggressive or territorial fish species
  • Fish that require different water conditions than the Pajama Cardinal

By carefully choosing tank mates that are compatible with the size, temperament, and behavior of the Pajama Cardinal, you can help create a peaceful and harmonious aquarium environment.

Advantages Of Having Pajama Cardinal In Your Tank

The first and most obvious advantage of having a Pajama Cardinal is its beauty. These fish are truly stunning, with their vibrant red and orange coloration. They will surely add a splash of color and excitement to any aquarium!

In addition to their beauty, they are also relatively easy to care for. They will thrive in your tank if you provide a clean, well-oxygenated tank and regularly feed them healthy foods like algae wafers or flake food.

The best part about keeping them is that they are peaceful and social fish. This makes them ideal for community tanks, as they do not tend to cause trouble for other species.

Disadvantages Of Having Pajama Cardinal In Your Tank

One potential disadvantage of having a Pajama Cardinal is that they are timid fish. This means they may not be the best option for tanks with larger, more active fish species. In these tanks, the Pajama Cardinal may spend most of its time hiding and may not come out to eat or interact with other fish.

Another potential disadvantage of these fish is that they are susceptible to changes in water conditions. This means you must be extra careful when cleaning your tank or adding new fish, as even a tiny change in water conditions can stress them out.

Finally, they are not the easiest fish to breed. If you are looking for a “hands-off” fish species that will take care of itself, then the Pajama Cardinal may not suit you. However, if you enjoy taking an active role in your pets’ care and want to try breeding fish, the Pajama Cardinal is worth considering!

Wrapping Up

As you can see, many reasons exist to love the beautiful and peaceful Pajama Cardinal. Whether you are looking for an eye-catching addition to your aquarium or want to try breeding fish, this exciting species will surely delight you. So why wait? Start shopping for your Pajama Cardinals today!​

I hope this guide has helped you better understand and care for your Pajama Cardinal. Good luck with your fishkeeping adventures, and happy tank-keeping!​

Disclaimer does not intend to provide veterinary advice. We go to great lengths to help users better understand their aquatic friends. However, the content on this blog is not a substitute for veterinary guidance. For more information, please read our disclaimer.

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