News / Species Spotlight / Highly Underrated Fish - Pajama Cardinals (01/20/15)

Highly Underrated Fish - Pajama Cardinals

In The Wild

During the day Sphaeramia nematoptera will school among and around branching corals, in mangrove roots and other similar, cover bearing structure. They can also be found singly and in pairs, discrepancies in the descriptions of wild behavior may be due to locality, spawning behavior or even time of day. During low light periods and at night, they break up their aggregations to hunt. There are reports of them being mixed into large aggregations of Orbiculate Cardinals (Sphaeramia orbicularis). They range throughout the tropical Indo-Pacific ocean and generally live in less than 50 feet of water. They are generally not found west of Borneo.

Like most (perhaps all) Cardinal fish, Sphaeramia nematoptera are mouthbrooders. Females can drop up to 8000 eggs per laying, much more than some other popular cardinalfish like Banggais. Males will then incubate these eggs for 8 days. When hatched, the larvae are less than 4mm long. Even at adulthood, this is a small fish attaining a maximum size of around three and half inches; they will attain this size for the home hobbyist as well, though it may take several years.

In the Aquarium

These are amazing aquarium fish. They are the picture of hardy and not very susceptible to most common aquarium ailments. They will generally eat just about anything you put into the aquarium, thawed meaty foods are favorite, and they can quickly be segued onto a high quality pellet. They will even eat bristleworms that are suspended in the water column. A widely varied diet will help ensure brilliant coloration throughout their lives. These cardinals have a surprisingly large mouth, and can take down a much bigger meal than you would originally assume.

Most Cardinalfish are extremely peaceful and the Pajama Cards are especially so. They can (and should) be kept in groups where a social hierarchy will develop. That arrangement is generally maintained peacefully with minor nipping and fin flicking between individuals, where damage between the "combatants" from this is extremely rare. They are totally reef safe, being extremely unlikely to bother any of the desirable invertebrates in their aquarium, with the possible exception of very small ornamental shrimps.

This is a shallow water fish that lives among branching corals (especially of the Porites genus) so you would expect them to be acclimated to very bright lighting conditions, but they are most active in low light periods, and will definitely prefer lower light areas of your display. Building large overhangs into the rockwork is a great way to keep them happy and active during the day in brightly lit aquariums. Because of their propensity for nocturnal feeding, I suggest at least one feeding before lights are on or after they are out. A timed pellet feeder works quite well for this.

A happy population of Pajama Cardinals containing both sexes will frequently spawn for home aquarists. There is some morphological differences between the sexes during spawning times, they can't be reliably be differentiated before that point. The best way to ensure having both males and females is to keep at least 6 of them together. Like nearly all cardinalfish (the notable exception being Banggais), these larvae do have a pelagic period. It is not insurmountable at 30 days, and successful rearing of the fry been done by many hobbyists and professionals alike. Aquacultured Pajama Cardinals are available from our stocklist.

Allen & Erdmann, Reef Fishes of The East Indies v1, 1st ed. (Tropical Reef Research, Bali, Indonesia, 2012).
Scott W. Michael, Reef Aquarium Fishes, 500+ essential-to-know species, 1st ed. (T.F.H. Publications, Neptune City, NJ, 2005)
Matthew L. Wittenrich, The Complete Illustrated Breeder's Guide To Marine Aquarium Fishes, 1st ed. (T.F.H. Publications Inc, New Jersey, 2007).
In House Refereces: Eli Fleishauer, Adam Mangino