Wow, sorry to hear about your new lion, I did read your post yesterday on it.......
Actually this is probably nothing you did or with your tank. Lions do not ship well really, if you do decide to go with another lion make sure it has been at your LFS 7-10 days before bringing it home. Have them hold it for you but not feed it for you, go in buy ghost shrimp, gut load them yourself or even try to wean the lion onto frozen foods during this holding time. If it is a LFS you deal with often they won't mind, Oh I drive mine crazy when I buy a lion.....lol
Do you know how long they had it before bringing it home?
Was the lion in quarantine?
What else did you have in the tank with this lion?
Did you or your LFS net this lion?
Kaye