CPR's AquaFuge hang-on refugiums come in three different sizes to meet the needs of marine aquarists. Each model comes with its own powerhead and features a unique baffle system that prevents the substrate and organisms from being disturbed yet also allows enough water to flow through the eliminate any stagnant areas. The AquaFuge provides ideal growth conditions for food items, such as copepods and ampipods, to feed invertebrates and fish in the main tank. It provides a controlled growing area for macroalgae, which can be used to reduce "nuisance" algae in the main tank and provided a "nursery" area for a variety of organisms. Includes Powerhead Water Capacity: 2.50 Gallons Dimensions: 13.5" L x 4.5" W x 12" T