Micro floras, micro faunas and sponges can provide a valuable food source for hard to feed reef tenants such as angelfish, tangs, mandarin gobies, butterfly fish and larger invertebrates. CaribSea A.R.K. is the first complete refugium kit for marine and reef aquariums which caters to the growth of these hard to obtain, hard to produce, natural foods. Only the A.R.K. contains substrates from .1 mm to 125 mm long axis, creating a haven for not only denitrifying and nitrifying bacteria, but also benthic organisms such as copepods and decapods. The larger macro-pores created by the variety of calcium carbonate rubbles form a cryptic zone to encourage the growth of water purifying sponges and larger invertebrates such as shrimp, worms and serpent stars. Also inside, a 5 lb. bag of CaribSea Mineral Mud to be used around Caulerpa, Halimeda and other macro-algae plantings or anchors. The A.R.K. also contains a 4 ounce bottle of Purple Up, the only patented coralline algae growth accelerator and an 8 ounce bottle of Aqua biotic to aid in the start up of necessary water purifying bacteria. You will also find an 80 gallon dose of Bio-Magnet, which clarifies water and places bacteria within the substrate and filter media as needed.