Welcome to AA!
well, the general idea to lower you salinity is to add more pure water to dilute the salt. That being said, you can just add more freshwater to reduce the salinity in the tank.
If you run a sump, or something that has an ATO or other features that requires the operating water level to be at a set point, you're going to have to remove some water first, then replace with fresh water back to the operating point.
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