Originally Posted by Dlauber
yup...theres really no other way to do it
But I woudnt stop adding water until your tank was full, then if you need to remove some of it to add sand, you wont run short.
I agree, if you leave room for your sand and you come up short on water, then you'll either have to do my personal favorite and add more sand, or you're gonna have to adjust your SG again because of topoff. I would just remove as needed as said in the previous posts.
I would give it a day to let your salt mix get where you need it before adding sand.