QUICK STATS

Care Level: Easy
Diet: Carnivore
Temperament: Peaceful
Reef-Safe: Yes
Venomous/Toxic: No
Approximate Purchase Size: 1-2"
Approximate Max Size: Around 3-3.5"
Recommended Tank Size: 20-30 Gallons or Larger

PAJAMA CARDINALFISH

The Pajama Cardinalfish (Sphaeramia nematoptera), also known as the Spotted Cardinalfish, is a peaceful reef-safe fish known for its unusual pattern, calm behavior, and beginner-friendly care. It has a yellow-green face, silver body, bold dark mid-body band, and reddish-orange spots toward the rear. It looks like three different fish were assembled during a power outage, and somehow it works.

Pajama Cardinalfish are excellent choices for peaceful reef aquariums because they stay relatively small, are generally hardy, and do not require aggressive feeding competition to thrive. They often hover calmly in the water column, especially around rockwork, caves, or shaded areas. In other words, they bring movement without acting like they are late to a very important fish meeting.

This species is considered reef-safe and should not bother corals or most invertebrates. It can be kept singly, in pairs, or in small groups in larger aquariums. Groups may establish a loose hierarchy, but they are usually much calmer than many other community fish, which is apparently what passes for emotional maturity underwater.

Note: Image is a representation of what to expect. The fish you receive may vary slightly in size, color, markings, spot pattern, and overall appearance.

AQUARIUM REQUIREMENTS

AQUARIUM SIZE

A minimum tank size of 20 gallons or larger can work for a single Pajama Cardinalfish, though 30 gallons or larger is preferred for better stability, more room for tank mates, and small group housing.

For groups, a larger aquarium is recommended. Pajama Cardinalfish are not hyperactive swimmers, but they do appreciate room to spread out, hover, and retreat into shelter when needed.

HABITAT RECOMMENDATIONS

Pajama Cardinalfish do best in established aquariums with live rock, peaceful tank mates, and areas of shelter.

Aquascaping: Provide live rock, caves, overhangs, and shaded areas. Pajama Cardinalfish often hover near shelter and may retreat into rockwork when startled.

Substrate: Sand, fine aragonite, crushed coral, or bare-bottom systems can all work. This species does not rely heavily on the substrate.

Rockwork: Live rock is strongly recommended. It provides shelter, biological filtration, and structure for natural hovering behavior.

Tank Maturity: A mature aquarium is preferred. Stable water quality and an established feeding routine help this peaceful fish settle in and maintain good body condition.

Tank Cover: A tight-fitting lid is recommended. Cardinalfish are not the most dramatic jumpers, but fish as a category remain committed to making bad vertical decisions.

WATER PARAMETERS

Pajama Cardinalfish are hardy once established, but they still need clean, stable marine conditions. “Beginner-friendly” does not mean “compatible with whatever chemistry tragedy is happening this week.”

Temperature: 72-80°F
pH Level: 8.1-8.4
Salinity: 1.020-1.026 specific gravity
Ammonia, Nitrite, and Nitrate: Ammonia and nitrite should remain undetectable. Nitrate should be kept as low as reasonably possible, ideally below 20 ppm.
Water Flow: Low to moderate flow is ideal. Provide enough movement to keep the aquarium oxygenated and move waste toward filtration, while still allowing calmer hovering areas near rockwork.

DIET

Pajama Cardinalfish are carnivores that should be offered a varied diet of small meaty marine foods. They are usually not difficult to feed once settled and often accept frozen and prepared foods readily.

PRIMARY DIET

Frozen Food: Offer mysis shrimp, enriched brine shrimp, cyclops, marine blends, finely chopped seafood, and other small frozen foods. We at Summit City Coral prefer frozen foods such as LRS Reef Frenzy and PE Mysis.

Prepared Foods: High-quality small marine pellets, flakes, and prepared carnivore foods can help provide balanced nutrition once the fish is eating reliably. Smaller food sizes are best.

Live Foods: Copepods, amphipods, live brine shrimp, and other small live foods can help encourage feeding, especially in newly introduced or shy individuals.

Small Meaty Foods: Finely chopped clam, shrimp, squid, and other marine foods can be offered occasionally for variety. Avoid oversized foods unless you enjoy watching a cardinalfish stare at dinner like it has been assigned homework.

FEEDING FREQUENCY

Feed small amounts 1-2 times per day. In community tanks, make sure food reaches the Pajama Cardinalfish before faster tank mates inhale everything like aquatic debt collectors.

COMPATIBILITY

Pajama Cardinalfish are peaceful and work well in calm community reef aquariums. They are best housed with tank mates that will not bully, chase, or severely outcompete them for food.

COMMON TANK MATES

Fish: Clownfish, gobies, blennies, firefish, peaceful wrasses, chromis, dwarf angelfish, anthias, tangs in larger aquariums, and other peaceful to semi-peaceful reef fish.

Avoid: Large predatory fish, aggressive dottybacks, overly aggressive damsels, triggers, groupers, lionfish, hawkfish large enough to eat them, and any fish likely to harass or swallow them.

Same Species: Can be kept singly, as a pair, or in small groups in larger aquariums. Groups may establish a hierarchy, so provide enough space and shelter.

Invertebrates: Usually safe with cleaner shrimp, hermit crabs, snails, urchins, and most common reef invertebrates. Very tiny shrimp or small crustaceans may be at risk, because small meaty snacks do not get legal protection in reef tanks.

Coral: Pajama Cardinalfish are considered reef-safe and should not bother soft corals, LPS, SPS, zoanthids, mushrooms, clams, or anemones.

BEHAVIORAL NOTES

Temperament: Peaceful and calm. Usually an excellent choice for community reef aquariums.

Activity Level: Moderate to low. Often hovers calmly near rockwork rather than swimming constantly throughout the tank.

Group Behavior: Can be kept in small groups in larger aquariums. They may form a loose hierarchy but are generally less aggressive than many other group fish.

Nocturnal Tendency: May become more active during lower-light periods, especially when first introduced.

Reef Compatibility: Excellent for reef tanks. They generally ignore corals and most invertebrates.

Mouthbrooding: Pajama Cardinalfish are mouthbrooders, with males carrying eggs in the mouth after spawning. Nature apparently decided parenting should include not eating for a while, which feels dramatic but effective.

Feeding Behavior: Usually accepts frozen and prepared foods once settled. Shy individuals may need food offered near their preferred hovering area.

Pattern Variation: Spotting, body band intensity, and coloration may vary slightly between individuals.

Jumping: A tight-fitting lid is recommended. They are not the worst jumpers, but the floor remains undefeated.

ACCLIMATION PROCESS

This acclimation method helps reduce stress by gradually introducing the fish to your aquarium’s temperature and water chemistry.

1. TURN OFF THE LIGHTS & ATO

Turn off aquarium lights to reduce stress. If you have an Auto Top Off system, switch it off before starting acclimation.

2. FLOAT THE BAG

Float the sealed bag in the aquarium for 15-20 minutes to allow the temperature in the bag to equalize with the tank.

3. OPEN BAG, ADD FISH TO CONTAINER

Carefully open the bag and transfer the fish and shipping water into a clean bucket or container.

4. ACCLIMATE USING TANK WATER

Add 1/4 cup of tank water to the container every 5 minutes for 40 minutes.

5. TRANSFER FISH TO AQUARIUM

Once acclimation is complete, gently transfer the fish into the aquarium using a net or specimen container. Discard the shipping water. Do not pour shipping water into your aquarium.

6. REFILL THE AQUARIUM WITH SALTWATER

You may need to replace the saltwater removed during acclimation with fresh mixed saltwater.