Frag Crate-Coral Propagation Grid is designed to optimize growing conditions for your propagated corals. It facilitates healthy growth by establishing unobstructed water flow and ease in moving your pieces to accommodate lighting requirements. Algae is less likely to accumulate on the all black structure and is visually appealing while it is securely and conveniently showcasing your coral frags in your aquarium. Frag Crate can easily be cut to any size or shape and combined to assemble into multiple layers or shelves. Non-Toxic and reef safe.