Most new tanks are not requiring any type of media in your filters at the beginning, these medias are used to remove unwanted things, and the only way to know if you have these unwanted things is to be testing for them each media removes a specific thing or multiple specific things and we won’t be sure what you need to remove unless it’s tested for. With that being said most saltwater tanks, as far as filtration go would be best to use some type of mechanical filtration, which is like a filter pad or sock to remove floating debris, and then secondly, is a skimmer, which does two things oxygenates the water along with removing scum and other things from the water
A new tank does not need gfo especially without testing
Welcome to R2R!
Filter-
Mechanical: filter socks, filter floss, filter sponges, skimmer
Chemical: Activated carbon, Granular Ferrous Oxide (GFO)
Biological: rocks/sand will host your nitrifying bacteria colonies.
