The river's gravel bed was gouged of trees by an angry flood two years ago.

Alternatively, you can add a natural regeneration zone to an existing pool by building a zone wall then adding a gravel bed and plants.

Beneficial bacteria colonize the gravel bed and provide biological filtration, using the substrate of the aquarium itself as a biological filter.

This led to the removal of the gravel bed, ties, and tracks.

The species constructs a nest or redd in the gravel bed of a stream.