For submersed aquatic weeds, herbivorous (plant-eating) fish are an attractive alternative to herbicides and other temporary methods of weed management. This type of biological control often requires less labor, fewer treatments, and less expense than other methods, and it has good potential for long-term management of aquatic vegetation.

Occasionally, the blue tilapia (Tilapia aurea) has been used to control algae, and the redbelly tilapia (Tilapia zillii) has been used to control aquatic macrophytes (coarser vegetation) in North Carolina. Because tilapia are tropical species and cannot tolerate water temperatures below about 50deg.F, they are unable to survive normal winter temperatures and have limited use for weed control in North Carolina. Common carp (Cyprinus carpio) and several variants of this species (for example, Israeli carp) have also been used for weed control. In most situations, these fishes have not been very effective, as they are omnivorous (eat a variety of foods) rather than strictly herbivorous. In cases where they have been effective, most of the control has resulted from their habit of muddying the water while rooting in the pond bottom for food, rather than from the actual consumption of vegetation. The triploid sterile grass carp (Ctenopharyngodon idella)is the primary fish used for the biological control of aquatic vegetation in the United States.

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