Read a lot of books, and listen to the experts!
Niger Trigger - 6"
Snowflake Eel - 8"
 Cleaner Shrimp - 2"
Coral Banded Shrimp - 2"
Tiger-Striped Star - 6" diameter
Sand-Sifting Star - 4" diameter
Various hermits and snails - 0.75-2"
Life's an ocean, dive it.
I'm 14 years old and love the saltwater hobby! Not much of a freshwater person, but I do breed Orange Sunshine Guppies.
The pet trade gets a bad rap for exploiting wild animals but sometimes the opposite is true.
Modern advances in technology affect every industry - even the aquarium hobby.
If you are looking for a unique invertebrate to add to your saltwater tank, consider the sea urchin.