Sand

It's sometimes nice to use cosmetic sand to create a path  in part of our aquascape.

For convenience, many aquascapers nowadays just layer sand thickly over aquasoil in areas where they require cosmetic sand. The sand layer must be thick enough so that the aquasoil doesn't float up. Hardscape is usually used to border the sand.

The other way is to line the path with rocks/coarse gravel, which forms a heavier boundary keeping both areas apart. It's then very useful to have smaller pieces of stone that fit between the larger pieces.