A refugium is nothing more than a refuge from predation. Sessile inverts, macroalgae and other delicate species need a place to call their own and the advent of the refugium was just the ticket! Isolated, but connected to the main display tank, the refugium allows for common water filtration while at the same time keeping more aggressive fish from impacting it. Refugiums have been found to be an excellent platform for cultivating high quality food sources (amphipods, copepods and macroalgae) in a separate but still attached system.
There are a number of macroalga (seaweeds) species which consume Nitrates (NO3) and Phosphates (PO4) at an astonishing rate. Macroalgae also make great food for fish and invertebrates in your saltwater aquarium. These seaweeds are perfect for cultivation in a refugium.