Refugium Rubble is a great way to add surface area to your sump or refugium. Many people do not like the look of small rocks the size of marbles to golf balls within their main display tank, yet this is an excellent home to many invertebrates that provide a valuable service to the reef tank. By adding the extra rooms per say within your aquarium, you are allowing a wider biodiversity to inhabit your aquarium. A greater variety of mouth sizes, ensures a more complete breakdown of food particles, waste etc.=== ===By adding this refugium rubble to your sump or refugium, you will be able to cultivate necessary food sources like amphipods and copepods which picky eaters find irresistible!!