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The Problem Nuisance algae often degrade water quality and the aesthetics of a pond or lake. The casual observer out for a stroll or jog 21 become toxic and cause oxygen deple- tions in the water when they die and decompose. Also, very few herbicides are labeled for use in water; in many ar- eas, herbicides carmot be used. The Exotic Algae Eaters DAVINE LIEBERMAN and JOAN THULLEN Applied Sciences Branch would likely notice unsightly green mats on the water's surface, grasslike clippings throughout the water column, or long green strands clumped together in a large mass. All of these factors may contribute to taste and odor problems in the water, low dissolved oxygen concentrations, toxic ammonia levels that can be deleterious to fish, obstruction of waterflow, and worst of all- management dilemmas. Nutrient-rich waters often exhibit algal or phytoplankton (free-floating micro- scopic flora) problems. Nitrogen and phosphorus concentrations provide suitable nutrients for rapid growth and massive blooms of algae, which then die off, repro- duce, bloom, and die off, all in a matter of days. When nutrients become limited or de- pleted, the magnitude of the algae cycle will wane; otheIWise, the blooms can cause major problems. Typical Solutions Traditionally, the control of nuisance algal growth has been achieved by (1) using chemical herbicides, (2) restrict- ing nutrient inputs, and (3) flushing ponds with fresh water. These expensive methods offer only temporary solutions to algal problems: . Chemicals, such as copper sulfate, are commonly used to reduce phytoplank- ton, but often add to the water quality problem. Algae such as blue-greens can . Nutrient restriction is usually not feasi- ble and is difficult to implement in most situations. . Flushing with large quantities of fresh water is wasteful, costly, and can cause severe pollution in receiving waters. A New Technique WATER (Water Technology and Envi- ronmental Research) projects EEOIO (Water Quality Protection and Enhance- ment) and EEOO? (Aquatic Site Pest Management) include environmental objec- tives that protect and enhance water quality in reservoirs, ponds, and canals by investi- gating new techniques and guidelines for controlling toxic and nuisance algae in the Western United States. New biological con- trol methods need to be feasible, cost-effective, and successful in control- ling the problem. Grass carp (Asian carp) have been used successfully by Reclama- tion scientists in the Environmental Sciences Section (Applied Sciences Branch) to control nuisance aquatic macro- phytes in irrigation systems. Unfortunately, macrophytes are quite dif- ferent in physiological makeup than algae. Grass carp prefer feeding on weeds rather than algae, therefore, taking care of one problem and not the other.