Bare Bottom
Easiest to clean, best for water quality, no digging drama.
Most serious show keepers use bare bottom. Add a dark back/bottom to compensate for stark look.
Sand
Natural look, soft on fish. Flowerhorns enjoy sifting through it.
Requires regular fluffing (Malaysian trumpet snails or manual stirring) to prevent dead zones.
Gravel
Easier to vacuum than sand, but flowerhorns scatter it aggressively.
Smooth rounded gravel only — sharp pieces damage fins and mouth.
My Recommendation
Competition/breeding: bare bottom.
Display tank with planned landscape: fine sand with scattered larger rocks.
Casual home tank: smooth gravel.