A Refugium is a contained "Place of Refuge" where conditions are optimized to promote photosynthetic organisms to flourish. This method isolates and utilizes algae to consume nitrate, and then produces glucose and oxygen. This creates a stable environment necessary for all aquarium inhabitants. View the 2 styles below.
Refugium Add-On Expansion Units are designed to cultivate plants and algae inside the refuge unit. They can operate as free standing units or be fitted inside a Wet Dry Filter Sump.
There are two standard sizes of the Refugium Expansion Unit:
The 2210 Refugium Expansion Unit : 3.5 Gallon Capacity
The 2220 Refugium Expansion Unit : 6 Gallon Capacity