The Pajama Cardinalfish is favorite with nano reef tank hobbyists due to their small size and temperament. Pajama Cardinalfish originate from the Coral Sea in the Indo-Pacific area and can be found in areas around Northern Australia, Papua New Guinea, the Philippines and Indonesia. Pajama Cardinalfish are naturally quiet and shy, tend to favor hanging out in the shadows. They should get along with most other species and will leave the saltwater invertebrates in the tank alone.
Pajama Cardinal Fish get to be about 3 inches (8 cm) in size and should do well in at least a 30 gallon tank or larger. You can keep them in groups but watch for aggression amongst them as they grow and start to pair off for breeding.
Another interesting fact about the Pajama Cardinals is that they are mouth brooders. After the eggs are fertilized the male picks them up and guard the eggs in his mouth until they hatch. After the eggs hatch the male “spits out” the juvenile fish and they are on their own.