If there is no livestock, which it sounds like this is the case, I definitely don’t see any apparent negative effect. Dont recommend it when the tank is up and running with other livestock, such a rapid salinity change can create problems.
So the tank has dry rocks and dry sand in it no livestock.
should I add the salt to the sump return area or should I mix a 5-gallon buck of high salinity? and add it to the return area of the sump, let the return pump it to the DT?