Pure sand and orchids seems like a bad call. Pure sand, orchids and semi hydro = death.
There are probably a few species of plants that might handle it, but the medium would become extremely anoxic in all but the smallest pots. Not sure the dampness will help your succulents either. Anthuriums strike me as quite happy in damp media.
There's a reason most hydro and semi hydro media have so much void space.
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