Pajama Cardinal (Sphaeramia Nematoptera): Ultimate Care Guide

The Pajama Cardinal is a small saltwater fish with a very distinctive look. These fish are native to the Indo-Pacific and Western Pacific regions. You can find the Pajama Cardinal in waters along the Southern coast of Asia all the way to the island of Fiji.

Pajama Cardinals are popular for their unique coloring and patterns. They have small bodies and two dorsal fins, as well as pectoral and pelvic fins. A thick black stripe runs along the middle of their body, from the first dorsal fin to the pectoral fins. Their face is a yellow or green color, and they have large orange eyes. The back of their body is a white or silver color patterned with red or orange polka dots. Other common names for this species include Spotted Cardinalfish or Polka Dot Cardinalfish.

The Pajama Cardinal is a reef safe fish. This species is peaceful towards fish, coral, and other marine invertebrates.

Pajama Cardinal Care

Pajama Cardinal fish are an easy species to care for. They are hardy fish and have a peaceful temperament. The Pajama Cardinal is a great choice for anyone new to fishkeeping.


The Pajama Cardinal is native to tropical regions and prefers warmer temperatures. Keep your Pajama Cardinal in waters that are between 72°F and 80°F. Aim to keep the temperature consistent as sudden changes can shock the fish and cause harm.

Water pH

Pajama Cardinals require water that is alkaline. Keep the water pH levels between 8.1 and 8.4.

Pajama Cardinal (Sphaeramia Nematoptera)
Pajama Cardinal (Sphaeramia Nematoptera)

Pajama Cardinal Size

The Pajama Cardinal can grow up to 3 or 3.5 inches in length. Many Pajama Cardinals are 1 or 2 inches when purchased, so it will not take long for them to reach their full size.

Food & Diet

The Pajama Cardinal prefers a specific diet. This species is carnivorous and feeds on live foods in the wild. To mimic this, feed your Pajama Cardinal small meals frequently throughout the day 4 to 6 times a week. Choose meaty foods, preferably live, although frozen or freeze-dried can be used. Some foods that are beneficial to include in the Pajama Cardinals diet are brine shrimp, mysis shrimp, feeder shrimp, and bloodworms.

Pajama Cardinals can also receive supplementation through high-quality flake or pellet foods. Some Pajama Cardinals may be picky about these foods or may need time adapting to them.

Pajama Cardinals are also nocturnal, hunting and eating at nighttime. You may feed them at night when they’re active or you need to train your fish to eat in the daytime.

Pajama Cardinals are slow swimmers so avoid tank mates that are faster than them. Fast swimming fish may steal food from the Pajama Cardinals before they can get to it.

Pajama Cardinal Lifespan

In the wild, Pajama Cardinals can live for about 1 to 2 years. When kept in captivity, these fish have a longer lifespan, living up to 5 years.

Pajama Cardinal Tank Size

Keep your Pajama Cardinals in a tank that is at least 30 gallons. This species is a schooling fish and is often kept with other fish. A 30-gallon tank will be enough if you keep your Pajama Cardinal in a small school. If you opt to keep your Pajama Cardinal with a large school, you must use a larger tank to provide enough space.

Tank Setup

Pajama Cardinals hide during the day and become active at nighttime. Providing plenty of places for them to hide in will allow your fish to feel safe and comfortable. Pajama Cardinals enjoy having corals, caves, rocks, and plants to hide around. In the wild, this species often hides in seagrass so adding some to your tank is ideal.

Pajama Cardinals do claim territory. They will likely choose a specific hiding spot that is “their home”, that they will return to regularly.

Pajama Cardinals tend to swim in shallow waters and will usually stay near the middle of the tank. Because of this, you can use any substrate within their tank.

The Pajama Cardinal fish prefers fast and strong water flow, so use a strong water filter. Your filter will also maintain clean conditions inside the tank. However, keep an eye out for excess food or debris that may be floating around and clean out as necessary.

Due to being a nocturnal species, the Pajama Cardinals require low lighting. Using moderate or bright lights may be harmful to your fish.

When bringing a Pajama Cardinal into a new tank, avoid placing them directly into the tank. Instead, drip acclimate them for about an hour to avoid shocking the fish and causing harm.

Pajama Cardinal (Sphaeramia Nematoptera)
Pajama Cardinal (Sphaeramia Nematoptera)

Pajama Cardinal Breeding

Pajama Cardinals are an easy species to breed. They are a mouthbrooding fish. The males will keep the fertilized eggs inside their mouth until hatched.

The Pajama Cardinals will not need a separate breeding tank like some species do. However, we recommend feeding high-quality live foods to the fish for several months leading up to breeding season. This allows the Pajama Cardinals to better prepare for spawning.

If you want to breed your Pajama Cardinals, keep 4 to 6 fish of mixed gender in your tank. Once matured, the fish will pair and begin breeding. The male fish will not eat while they keep the eggs safe inside their mouth. During this time, the females will protect them.

After hatching, the fry will be free swimming right away. Feed the fry with rotifers, amphipods, or baby brine shrimp.

While Pajama Cardinals are generally a peaceful fish, they can become aggressive in breeding season. Once two have paired, they become aggressive towards other Pajama Cardinals. It is important to monitor the fish, specifically males, for aggressive and hostile behavior.  

The male and female Pajama Cardinal can be difficult to tell apart. As they mature, the males will become slightly larger than the females. The sex of each fish will become obvious during breeding season. The female fish will have larger abdomens from carrying eggs, while the male fish will later scoop up and carry the fertilized eggs.

Pajama Cardinal Disease

Since Pajama Cardinals are a hardy fish, they are not easily susceptible to disease. However, when given improper care, these fish can experience infections and other issues. Here are some common saltwater fish diseases to look out for:


Dropsy is a bacterial infection that manifests as a swollen or bloated fish. Another symptom is raised scales, sometimes referred to as “pinecone scales”. This infection comes from poor water quality. Improve conditions in the tank by ensuring there is no floating debris, and doing a water change of 25%. Maintain these improved conditions over the course of a week or two. Change the water again as necessary. If your fish is still sick, use over the counter medication to treat them.

Hole in the Head (HITH)

Hole in the Head is a disease caused by Hexamita, a parasite that often lives within fish. Hexamita is typically dormant. However, when the immune system of the fish weakens, the parasite can attack the fish. HITH is exactly as it sounds; the disease appears as holes in the fish’s head. Take your fish to a veterinarian immediately for prescribed medication. You should also look for what weakened the fish’s immune system to begin with. Poor water conditions or lack of proper nutrition are common culprits.

Ich (Ick)

Ich is another disease caused by parasites and a weakened immune system. Typically with Ich,  it is stress that causes the immune system to weaken. Ich is noticeable by the small white spots that spread across a fish’s fin and body. Quarantine your fish and purchase over the counter medication, following the directions provided. Monitor your fish to find the cause of the stress and prevent any more infections or diseases.

Pajama Cardinal School

The Pajama Cardinals are a schooling fish and prefer to be in groups. Being kept in a school of at least 6 or more other Pajama Cardinals is ideal. Although, you can keep only one or two if you have a smaller tank.

As mentioned above, the male fish can become aggressive during breeding season. Outside of that, these peaceful fish enjoy being with their own kind and feel safer together.

Pajama Cardinal Tank Mates

Pajama Cardinals are very peaceful, and even passive, fish. They will easily get along with other fish that are calm and peaceful as well. Avoid placing them with predatory fish. Predatory and aggressive fish, especially those larger, may attack your Pajama Cardinals. Also, avoid having fast swimming fish as tank mates for the Pajama Cardinal. Fast swimmers may frighten them or cause stress.

Some compatible tank mates for the Pajama Cardinal include:

  • Gobies
  • Firefish
  • Dart fish

Some incompatible tank mates for the Pajame Cardinal include:

  • Clownfish
  • Angelfish
  • Lionfish

Pajama Cardinals are also compatible with corals. They will not attack the corals and will enjoy hiding amongst them.

Stress may cause Pajama Cardinals to lose color. If you notice dull coloration on any of your fish, ensure that their tank mates are suitable for them. If the other Cardinals or other species are not the issue, make sure the tank is a suitable size for the amount of fish you have.

Where Can I Find Pajama Cardinal for Sale?

Pajama Cardinals may be difficult to find in your local pet stores, you can call to ask before you go in. However, you can find this species for sale on specialty websites. Expect to pay between $20 and $40 for you Pajama Cardinal. The price ranges based on the size and origin of the fish you are purchasing.

Pajama Cardinal vs Banggai Cardinal

Pajama Cardinals and Banggai Cardinals are both small saltwater fish from the family Apogonidae. They have similar body types and generally grow to the same size. However, these fish have very different coloration and patterns.

Banggai Cardinals are native to a small group of islands in Indonesia. They have silver bodies with three vertical black stripes on their body. Their fins and parts of their body are covered in small white dots.

The general care and maintenance required for these species is the same. However, Banggai Cardinals are a more aggressive species. They are territorial and become aggressive towards the same sex, specifically in breeding season. Aim to keep no more than one of each sex together.

The Banggai Cardinal is also an endangered species. Avoid purchasing wild caught Banggai and opt to buy captive bred instead.

Leave a Comment

Your email address will not be published. Required fields are marked *