Probably not the fish but it will inverts. Fish can take lowering the salinity pretty quick but not so much raising it. So raise it slow back to where it was over a few days
Fish can take a reasonable decreases in salinity with out a problem. Say a drop from 1.026 to 1.020 should be OK. You want to increase in very slowly though as they can't take a fast increase.
You didn't mention the original vs current salinity. The best option is to just topoff with full strength saltwater instead of fresh water. If you could post actual salinity levels that would help.
