Ppl who say scrape it off "LEFTY
" IMO are kinda right. I know the salt came from the tank and you took water "or it splashed" out of the tank and eveporated leaving behind the salt. Now if you dont place it back in the tank and you just fill it up with freshwater you are actually gonna "overtime" end up with a very low salanity. We all know that isnt very good.
Now if you have some freshwater in hand and place it back in the tank it would be just like the saltcreep was never there. If you place the water in the tank and put the salt back then the salanity "in theory" would be were it was when you started.
Now for the kinda right thing. If you place the salt back without freshwater then the salanity will rocket where you dont want it. And we all know that isnt good either.
Sorry for the long book I posted but IMO I would fill the tank back up and place the salt back in.