Recirculating aquaculture systems (RAS) are designed to recondition "used" fish water so that it can be recycled back into the fish-rearing tank(s). These systems have become popular because of the ability to control water parameters, their high-density rearing capabilities, and their potential for water conservation. Because of the accumulation of nutrients in these systems, they offer an underutilized resource for persons willing to transform an existing RAS into one that integrates plants. A secondary crop of plants can add to the system's profit, with little overhead cost. The reduction of certain nutrients by the plants can also benefit the system by reducing or eliminating expensive filtration components. These integrated systems have gained recognition by researchers and commercial users alike, and have stimulated the interest of many because of their resource-efficient and "eco-friendly" status.