Well, we would have to know your tanks water parameters and your method of acclimation to try and tell if it was perhaps something you could have fixed. If the fish was fine at the lfs
, it sounds like an acclimation problem. Most lfs
keep their salinity very low, so all fish need a slow acclimation to raise the salinity and adjust to the new ph
of your tank.
Also, it's a long shot but, did you see any aggressive posturing from the lion? They aren't normally aggressive but if it's been in the tank awhile by itself, it may become territorial or may have even poked the trigger on accident. This isn't likely the cause but thought I'd mention it just the same.
Also, you were correct in not adding the lfs
water to your system.