Fellow Creatures
Saltwater Fish

Pajama Cardinalfish

Sphaeramia nematoptera

Peaceful nocturnal cardinalfish that lives in groups  ·  Beginner

Pajama Cardinalfish

Brian Gratwicke · CC BY 2.0 — Wikimedia Commons

Lifespan
4-5 years
Adult size
8 cm (3 in)
Min. habitat
Aquarium 110L+ / 30gal+
Social needs
Shoaling; keep in a small group
Diet
Carnivore (mysis, brine, frozen, pellets)
Time
Daily feeding; weekly testing/changes
Cost
Medium

Overview

  • The Pajama Cardinalfish has a silver-yellow face, a dark band across the body, and a polka-dotted rear, giving it a mismatched "pyjama" look.
  • It is peaceful, hardy, and reef-safe, and unlike most cardinals it does well living in a group, hovering together in the open during the day.
  • Naturally nocturnal, it becomes most active at dusk but adapts to feed during the day in aquariums.
  • Its slow, gentle drifting makes it a distinctive addition that contrasts with more active swimmers.

Housing

  • A cycled 110L (30 gal) or larger tank lets you keep a small group among live rock and branching coral cover.
  • Maintain salinity 1.024-1.026, temperature 24-27°C (75-80°F), pH 8.1-8.4, and nitrate low.
  • Moderate flow and a covered top are best.
  • Provide overhangs and branching structure where the group can rest and feel secure.
  • Stable, clean water and ample cover keep these gentle fish confident and out in view during daylight hours.

Diet

  • The Pajama Cardinalfish is a carnivore.
  • Offer frozen mysis and brine shrimp, finely chopped seafood, and small marine pellets, fed once or twice daily.
  • Being naturally nocturnal, some appreciate a feeding near dusk.
  • They can be timid eaters, so make sure boisterous tankmates do not take all the food first.
  • Target-feeding shy individuals helps them keep weight.
  • A varied meaty diet maintains their condition and gentle, hovering activity.

Health

  • Pajama Cardinalfish are hardy and disease-resistant in stable water.
  • The main risks are stress from aggressive tankmates, underfeeding when outcompeted, and marine ich following poor quarantine or unstable parameters.
  • Quarantine new fish, keep nitrate low, and watch for thin bellies or hiding, which suggest a fish is not eating enough.
  • A peaceful tank with good cover and reliable feeding keeps these fish in good health.

Temperament

  • Peaceful, slow-moving, and reef-safe, the Pajama Cardinalfish is harmless to corals and most invertebrates, though very small shrimp may be eaten.
  • It does best kept in a small group rather than alone.
  • Lone fish tend to be reclusive, while a group of three or more drifts confidently in the open.
  • Pair them only with calm tankmates, as fin-nippers and aggressive fish will keep them hidden and stressed.

A good fit for

  • Beginners wanting a peaceful group
  • Reef community tanks
  • Keepers who like calm, hovering groups
  • Dusk-active display tanks

Common mistakes to avoid

  • Keeping just one (becomes reclusive)
  • Fast tankmates stealing their food
  • Pairing with aggressive or fin-nipping fish
  • Insufficient hiding cover causing stress
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