Just to add beyond making sure your have an accurate reading and that you lower it slowly:
To lower your SG
you remove about 1/2 to 1+ gal
of salt water from your tank and replace with fresh.
i.e. if you have a 30-55 gal
tank I'd remove 1 gal
, replace with FW
and recheck your SG
level. Then the next day do it again till you get your SG
level down to where you want it.
If you have a 75+ gal
tank you will need to remove 2+ gal
and replace with FW
to lower it so you notice.
Point is as already mentioned is to do it slowly so your stock has time to adjust. You want to drop (or raise it) about .002 per day i.e. if your SG
is 1.028 then a .002 drop moves it to 1.026
Lastly just like top off water the 1-2 gal
replacing the SW
does not need to be brought up to the same temp as your main since the small amount will have no effect on the main tanks temp.