i'd keep him on a clip, just because it allows you to check on the shark everyday and it keeps unwanted critters from checking out the egg.... you probably have some hitchhikers you dont know about (snails, bristles, others etc) that might eat their way into the egg case and cause the shark to die.
keep your snails in check, they WILL try and clean the "algae" off the egg case... which is not actually algae, its part of the case (cool fact, its made outta the same stuff as your toenails! LOL).. I kept algae sheets in mine just in case beause my turbos would start cleaning it at night... itkeeps them occupied and away from the egg.
be sure to pinch the end of the case, mostly where its pinched in the back, and how long did you acclimate the case? i did mine for almost 8 hours to get him all situated... just to be safe since the water is so much different than what hte LFS would most likely have.
good luck with this guy, they are pretty neat to have but also for the advanced aquarist... i didn't go for one until AFTER seven years of experience with just sharks lol.
btw, what its the temp of your tank? and can you post pics? :) i can prolly tell you how old it is and how long you have until it'll hatch with those facts :)