In the natural habitats of shrimps, you can always find leaves that are dropped into the streams and water bodies. The leaves decomposes over time, releasing its goodness of minerals, vitamins and at the same time, get munched on by the critters.
Natural Shelter of dried Cholla Catus, promotes microganism which is eaten by shrimps. Liked by plecostomus species too. Available in various length and shape.