Cardinal Fish are a great beginner saltwater fish. They are easy to keep, not aggressive and occupy the open water area of an aquarium. There are several varieties of marine cardinal fish like; Pajama cardinal, Stoplight cardinal fish, Banggai cardinal fish, and Flame cardinal fish just to name a few. Non of these saltwater cardinal fish will outgrow the home aquarium.
Saltwater Cardinal fish readily accept your standard marine aquarium foods such as brine shrimp, mysis shrimp and most flake and pellet foods. This makes them really easy to care for.
Cardinal fish also do well in groups where they will be a schooling fish. Also as far as saltwater fish go they are a cheaper saltwater fish so getting a nice size school will not break the bank.
Cardinal fish are also being captive bred. This increases their hardiness and ease of acclimation to the home aquarium.
In short saltwater Cardinal fish are a great aquarium fish for most any saltwater aquarium.