Greetings; here you will be introduced to a myriad of organisms suitable for keeping in small (forty gallons and less) marine systems; with pertinent critical notes on their selection, introduction and care. It is my earnest hope/desire that you be successful; and my further fervent belief that after a life time well-spent in the field that you will learn sufficiently through this exposure to be so. Sorting through all that's offered, available in the ornamental marine livestock trade is a daunting task; and one fraught with dangers... Many, most of the life offered is not "mix-able"; too much of it is unsuitable for small aquarium use. Not to worry There's still a huge assemblage of biota to discover, enjoy for you to choose from (or be chosen).