get some carbon running and change frequently , very large water change as well at this point.
remove any parts of the nem that are left and skim wet if you are running a skimmer.
not much else you can do but if quick you may save whats left.
im over at concept if theres anything i can do to help let me know and i will
good luck ive had it happen and im sure just about most have , its sad but at the same time is fixable.
call or pm me if you need more info 403-230-7831(concept aquariums)
cheers
denny