Acclimation Ammonia Confusion

[Randy Holmes-Farley]

Bringing this back up hopefully someone can help but what should one do when the salinity doesn’t match? I just got a fish at 1.018 and I run my tank at 1.026

My plan is to make new water at the same temp and salinity as the incoming water and immediately dump the fish (not any of the incoming water). Then you can adjust it in temp and salinity slowly.