No problem. What you run into a lot is people insisting you can keep brackish fish in freshwater, and technically you can....for a little bit. They'll survive....for a little bit. But the ones that need lower SG will be more prone to illness and die early, and the ones that need higher SG just won't make it long at all. There aren't many fish that do well in both--mollys are the only fish I've found that do fine in freshwater, brackish, AND saltwater if acclimated properly.