There are a couple of Cardinalfish species that are quite common in the aquarium trade including the Banggai Cardinalfish and the Pajama Cardinalfish. Others, such as the Flame Cardinalfish and the Longspine Cardinal are not very common. This group can be very interesting to keep and they stay on the small side only geting up to 2 or 3 inches as adults. They also can be a good first introduction to the breeding of marine fishes. The Banggai has been bred by hobbyists and professionals alike. This is a good thing for our hobby because the Banggai is threatened in it's natural habitat.
It is interesting to note that these Banggai Cardinal Fish are only found in a rather small area around Banggai Island off Sulawesi. This fish is very close to being placed on the endangered species list because of over collection. Before you purchase a Banggai Cardinal Fish, ask the retailer where they come from.
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.