Fresh to saltwater ??

[Atlantic]

Hello, i currently have a 75g tank set up and fully cycled for fresh water. I was waiting on a Jaguar cichlid to come into the lfs, but the other day they got in a spiny box puffer or striped burrfish whichever you like to call it

My question is will the tank need to be recycled or would it be safe to add salt, wait a week or so and put the puffer in? Or are the bacteria different in salt and freshwater?

Thanks for the help