Marco Rock Premium Shelf is one of our most popular rock offerings. Formed naturally from ancient reef structures, we hand select and process the most premium structures in the Marco Rocks line to create this natural aquarium rock offering. It lends itself to that perfect shelf scape that is reminiscent of a multi-tiered reef scene. We recommend stacking the rocks horizontally and cementing them together at key junctions with E-Marco-400 mortar. The natural color is perfect for new scapes, Coralline for established reefs or to blend perfectly with our new Coralline rock. For best results, place these rocks over our MR Foundation Rocks. Our MarcoRocks is the finest all natural aquarium rock available today, often featuring fossilized ancient corals within the rock.