Pajama Cardinalfish (Sphaeramia nematoptera) M

Overview

The Pajama Cardinalfish (Sphaeramia nematoptera) is a popular marine aquarium fish admired for its distinctive “pyjama” pattern, calm temperament and ease of care. With a silvery body, yellow tail and bold black spotting, it adds instant character to a saltwater display without the aggression often seen in many marine species. This medium-sized specimen is a great choice for reef and fish-only community aquariums where a peaceful presence is desired.

Native to sheltered tropical waters, this cardinalfish is best kept in a stable marine setup with plenty of rockwork and quiet tank mates. It is generally reef-safe and suitable for aquarists looking for a hardy, attractive fish that can become a long-term resident in a well-maintained aquarium. At Tropical Fish Co, all livestock is packed with care and supported by our live arrival guarantee and fast UK delivery.

Although peaceful, Pajama Cardinalfish are best kept in small groups or pairs where possible, as they naturally appreciate the security of conspecifics. They are nocturnal by nature and may spend much of the day hovering calmly in the water column or sheltering among rockwork, becoming more active as lighting dims.

Care at a Glance

Origin & Natural Habitat

Sphaeramia nematoptera is found across the Indo-Pacific, including areas around Indonesia, the Philippines and northern Australia. In the wild, it inhabits sheltered lagoons, seaward reefs and coastal areas with abundant coral cover and crevices. These environments provide protection from predators and plenty of small food items drifting in the water column.

The species is adapted to calm, structured habitats rather than open water. This is why aquarium setups with live rock, caves and shaded areas work so well. Their natural behaviour includes hovering in place, retreating into cover when startled and feeding on small crustaceans and zooplankton at dusk and night.

Tank Setup & Water Parameters

A mature marine aquarium of at least 120 litres is recommended for a single Pajama Cardinalfish, with larger systems preferred for a pair or small group. A stable environment is more important than a very large footprint, as this species values shelter and low-stress surroundings. Use quality live rock to create overhangs, caves and swim-throughs, while leaving open areas for gentle cruising.

Water quality should be excellent and consistent. Maintain a salinity of around 1.023–1.026 specific gravity, temperature between 24–28°C and pH in the range of 8.1–8.4. Strong, turbulent flow is not necessary; moderate circulation and efficient filtration are ideal. As with all marine fish, regular testing and routine maintenance are essential for long-term health.

Lighting can be moderate to bright, especially in reef aquariums, but ensure there are shaded retreats where the fish can feel secure. A tight-fitting lid is recommended, as cardinalfish may jump when startled. Provide a peaceful aquascape and avoid sudden changes in salinity, temperature or water chemistry.

For best results, acclimate slowly using a drip method and allow the fish to settle in without disturbance. Newly introduced individuals may hide at first, but they usually become confident once they recognise the tank as safe.

Feeding Guide

Pajama Cardinalfish are omnivores with a strong preference for small meaty foods. In captivity, they readily accept frozen marine foods such as mysis shrimp, enriched brine shrimp, chopped krill and finely minced seafood. They will also take quality marine pellets and flakes designed for carnivorous or omnivorous saltwater fish.

Feed small portions once or twice daily, offering food that is easy to swallow. Because they are not fast, aggressive feeders, it is best to ensure more boisterous tank mates do not outcompete them at mealtimes. Target feeding or feeding in a quieter area of the tank can help shy individuals thrive.

A varied diet supports colour, condition and long-term vitality. Occasional vitamin-enriched foods are beneficial, especially in mixed reef systems where natural grazing opportunities may be limited.

Tank Mates / Compatibility

This species is a superb choice for peaceful marine community aquariums. It coexists well with other calm fish and is generally reef-safe, making it suitable for many coral-focused setups. Ideal companions include clownfish, gobies, blennies, firefish, small wrasses with gentle temperaments and other non-aggressive cardinalfish.

Because Pajama Cardinalfish are slow and non-confrontational, avoid housing them with highly aggressive species, large predatory fish or very boisterous feeders that may stress them or prevent them from eating properly. They are best kept away from fish known to bully timid species, such as large damsels, triggerfish, puffers and many hawkfish in smaller systems.

They can be kept singly, as a pair or in a small group if the aquarium is large enough and well structured. In groups, provide plenty of hiding places to reduce any territorial behaviour. When introducing multiple individuals, do so carefully and monitor for dominance issues, especially in smaller tanks.

Why Buy from Tropical Fish Co

At Tropical Fish Co, we specialise in healthy, responsibly sourced aquatic livestock and aim to make marine fishkeeping straightforward and enjoyable. Your Pajama Cardinalfish is packed with care, dispatched with fast UK delivery and covered by our live arrival guarantee for peace of mind.

We understand that marine fish need excellent handling from the moment they leave our facility to the moment they reach your aquarium. That is why we prioritise careful acclimation guidance, secure packaging and reliable service. Whether you are building your first reef-safe community or adding a peaceful centrepiece to an established marine tank, we are here to help you choose livestock that suits your setup.

Choose Tropical Fish Co for quality fish, trusted service and support that continues beyond checkout.