Selecting plants as a decoration for a saltwater aquarium can be somewhat tricky since, in most cases, they're not typical "plants" at all, but rather algae. Algae have gotten a bad rap, particularly from freshwater hobbyists who lunge for an herbicide with the mere mention of the word. But algae are nothing more than non-flowering plants that usually grow in water. They are extremely hardy (among the oldest life forms on this planet) and require only good water quality and light, with nutrients being supplied from the waste products of your pets.
For more information, please read Selecting Plants For Your Saltwater Aquarium