There are many types of ...

There are many types of media bed materials available.  Making any recommendation will depend on the process for the desalination and the contaminants and concentrations.

For example if your process requires chemical oxidation prior to media bed filtration then the catalytic type media will be favourable.  If the project is economically savvy then the modern technology textile media bed filters present the best CAPEX and OPEX cost to performance ratio.  Textile media is also better performing in high turbidity so will provide a better performance when the sea water is turbid, such as during a climate event.

If the project already has sand filters and are wishing to replace the media then a review of the particle shape parameters is required.  Along with pressure differential limitations and pressure at discharge requirements.  The maximum sand media grain size will have a limitation relating to the back washing process, liekwise the minimum sand grain size will have limitation relating to the tank screens design

at a very basic level the physics of sand are independent of water chemistry, but over long operational life the mineralogy of the sand can show huge performance differences.