When buying coral frags online, be sure to ask if they are fresh cut or grown out. Fresh cut frags are just as they sound. The seller cuts a piece of coral off a larger colony and either tosses it into a bag or glues it to a frag plug before shipping it out. A mature, grown out frag is one that was cut weeks or even months ago. The coral has grown onto the frag plug to some extent, and is no longer relying on glue to hold it in place. Even though both types of coral frags can be shipped overnight with much success, a fresh cut coral frag will not handle the stresses of shipping as well as a matured coral frag. This can manifest itself in the bag, meaning it can die in the bag, or the stresses might not show up right away. The coral could sit in your aquarium for a day or two before completely bleaching out.