Cardinalfish

Pyjama cardinalfish

Sphaeramia nematoptera

Also sold as Pajama cardinal, Spotted cardinal

Good first fish

Pyjama cardinalfish (Sphaeramia nematoptera), photographed in the sea or an aquarium — Photo: Brian Gratwicke, CC BY 2.0, via Wikimedia Commons

Care level: Beginner
Adult size: 8.9 cm in aquariums
Minimum tank: 76 litres
Temperament: Peaceful
With corals: Reef safe
Captive-bred: Occasionally captive-bred
IUCN status: Least Concern

Show volumes inLitresUK gallonsUS gallons

How do you care for the pyjama cardinalfish?

Peaceful.

Feeding

Carnivore.

Most active at dusk; feed slowly sinking frozen food.

Tank and special needs

Plan for at least 76 litres of water (the care sheet says 20 US gallons).

Shaded spots.

Corals and invertebrates

None; may eat very small shrimp.

Which tankmates suit the pyjama cardinalfish?

Small group; slow, so avoid boisterous feeders.

Suggested order in a mixed tank: add early, with the first peaceful fish.

More than one pyjama cardinalfish

Best kept as a group added at the same time, in a tank big enough for the group.

Other fish

Checked against the other 59 fish in this guide, assuming a tank big enough for both. Individual fish differ, so treat this as a starting point.

Take care (3)

Maroon clownfishMaroon clownfish is aggressive and may bully the pyjama cardinalfish, especially if the bully is added first.
Humbug damselHumbug damsel is aggressive and may bully the pyjama cardinalfish, especially if the bully is added first.
Powder blue tangPowder blue tang is aggressive and may bully the pyjama cardinalfish, especially if the bully is added first.

Usually fine together (56)

Invertebrates

Only the invertebrates with a known risk are listed.

Take care (6)

Skunk cleaner shrimpPyjama cardinalfish may eat very small shrimp; adult skunk cleaner shrimps are usually safe.
Peppermint shrimpPyjama cardinalfish may eat very small shrimp; adult peppermint shrimps are usually safe.
Camel shrimpPyjama cardinalfish may eat very small shrimp; adult camel shrimps are usually safe.
Tiger tail sea cucumberA stressed or dead tiger tail sea cucumber can release toxins that harm fish; cover pump intakes.
Sea appleA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
Harlequin shrimpPyjama cardinalfish may eat very small shrimp; adult harlequin shrimps are usually safe.

Corals and anemones

Only the corals and anemones with a known risk are listed.

Take care (1)

Carpet anemones (Haddon's, giant)The carpet anemones (Haddon's, giant) can catch and eat small fish such as the pyjama cardinalfish.

These checks follow the reasons fish and invertebrates clash: same species or genus, similar shape, mouth size, temperament, food, burrows, tank size and the order they are added. Individual animals differ; every source agrees on that.

Quarantine and health

Standard.

New fish are the most common way disease gets into a reef tank. Quarantine every fish in a separate tank before it joins the display, and choose a method that suits its tolerance of copper.

Captive-bred or wild?

Some captive-bred supply.

Where sources disagree

Where sources disagree
Topic	What sources say	Our reading
Minimum tank	20 US gallons in the retailer quick stats. 30 US gallons for a group in the overview.	Use about 114 litres (30 US gallons) for a group.

Other minimum tank sizes we found:

The same page's overview recommends 30 gal for a small group.

What does it cost in the UK?

about £18. This is one UK retailer’s listing on 21 October 2026, not a market average, and every item was sold out on that day.

Sources

LiveAquaria (US retailer) care sheetRead 21 October 2026, read in full. Used for: stats.
FishBase species summaryRead 21 October 2026, read in full. Used for: max length, IUCN.
Kraken Corals (UK retailer) catalogueRead 21 October 2026, read in full. Used for: UK price.

Last checked 21 October 2026. How we check

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