PhosGuard rapidly removes phosphate and silicate from marine and freshwater aquaria. Although PhosGuard is effective in both fresh and marine water, it will operate better in sea water and the need for it is better defined in sea water. It is not recommended for phosphate buffered freshwater (PhosGuard would remove the buffer until saturated). PhosGuard is highly porous and bead-shaped to promote easy water flow through and around it, thereby increasing both its efficiency and capacity.