Take the LMB back to the fishstore. It's the only way you will keep it alive. Don't make it suffer. People tend to add LMB to the tank to early and because LMB rarely takes to prepared foods, without enough algae it will starve. Mine, fortunatly, eats the seaweed saoked in garlic, but I'm still keeping an eye on him. If you dod a search for LMB there are many post pertaining to them starving in a tank. Hope you make the right choice.
Jessica
New Orleans