Can I keep just one Pajama Cardinalfish?

Yes, a single Pajama Cardinalfish will usually adapt well to a peaceful community aquarium. However, keeping them in a group of five or more encourages their natural shoaling behaviour, makes them feel more secure, and provides a much better visual display.

Why is my Pajama Cardinalfish hiding during the day?

This is completely normal. They are naturally nocturnal fish that prefer to shelter in caves, overhangs, or among branching corals during the bright daytime hours, becoming much more active as the lights dim.

Will they eat my ornamental shrimp?

No, Pajama Cardinalfish have small mouths and are generally considered completely safe with popular ornamental species like Cleaner Shrimp, Blood Red Fire Shrimp, and Peppermint Shrimp.

Why does one of my cardinalfish have a swollen jaw and isn't eating?

If you have a pair or group, it is highly likely you have a male brooding eggs. Pajama Cardinalfish are paternal mouthbrooders; the male holds the fertilised eggs in his mouth for several weeks to protect them, during which time he will refuse food.

What should I feed them?

They are carnivores that thrive on small meaty foods. Offer a varied diet of frozen Mysis shrimp, enriched brine shrimp, Calanus, and high-quality marine pellets. Feeding them near the end of your light cycle will yield the best feeding response.

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Pajama Cardinalfish

Sphaeramia nematoptera

The Pajama Cardinalfish is a peaceful, strikingly patterned schooling fish that makes an exceptionally hardy addition to any marine aquarium.

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Ideal Conditions

Temperature: 24 – 28 °C
pH range: 8.1 – 8.4
Hardness: 8 – 12 dGH
Salinity: 1.023 – 1.026 SG
Adult size: 7 – 8.5 cm
110L (minimum for a small group): 110 litres+
Lifespan: 5 – 8 years
Diet: Carnivore
Water flow: Low to moderate
Preferred setup: Live rock structures featuring overhangs, caves, and crevices to provide shaded areas for daytime resting. Branching corals (or synthetic equivalents) are highly appreciated.

About the Pajama Cardinalfish

With its quirky pattern of polka dots, bold stripes, and a greenish-yellow face, the Pajama Cardinalfish is a visually unique staple in the marine hobby. Belonging to the family Apogonidae, these fish are largely nocturnal in the wild, spending their days hovering in loose aggregations among branching corals or rocky overhangs. They are slow-swimming, deliberate fish that add a tranquil, fascinating dynamic to reef aquariums.

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Is it right for your tank?

Check Pajama Cardinalfish against a habitat you already keep. We compare water type, temperature, pH, adult size, group needs and everything living there.

Where Pajama Cardinalfish comes from

Native range

Western Pacific Ocean

Countries / regions

Indonesia, Fiji, Australia, Papua New Guinea

Habitat

Sheltered coastal bays, lagoons, and coral reefs, often found sheltering among branching corals or mangrove roots during the day.

Widespread throughout the Indo-Pacific, primarily clustered around the Coral Triangle and northern Australia.

Similar species

Banggai Cardinalfish
Pterapogon kauderni
Yellowstriped Cardinalfish
Ostorhinchus cyanosoma
Longspine Cardinalfish
Zoramia leptacantha

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

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Ocellaris Clownfish
Amphiprion ocellaris
Peaceful and occupies different areas of the aquarium, making them completely compatible.
Great
Firefish Goby
Nemateleotris magnifica
A similarly peaceful, reef-safe species that thrives in the same water conditions and will not bother the cardinalfish.
Great
Cleaner Shrimp
Lysmata amboinensis
Pajama Cardinalfish pose no threat to ornamental shrimp and will often benefit from their cleaning services.
Great
Six Line Wrasse
Pseudocheilinus hexataenia
Can become highly territorial in smaller tanks and may harass the docile, slow-moving cardinalfish.
Compatible with caution
Lionfish
Pterois volitans
Predatory and will easily swallow a Pajama Cardinalfish whole.
Not recommended

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