This 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 the Premium Shelf Rock for your aquarium. It lends itself to that perfect shelf scape that is reminiscent of a multi-tiered reef scene. We recommend stacking the rocks as horizontal as possible and cementing them together at key junctions with our E-Marco-400 mortar. Natural color is perfect for new scapes, Coralline for established reefs or to blend perfectly with our new Coralline rock. To help disguise the joints, consider using our MR Powder. For best results, place these rocks over our MR Foundation Rocks. Our MarcoRocks is the finest all natural aquarium rock available to the aquarium enthusiast today. It is a once live natural reef rock. All natural calcium carbonate rock. Never any chemicals, additives. Often, you can spot fossilized ancient corals within the rock. Highly Porous and Beautifully Shaped