Shallow lake restoration is a pilot research in Environmental Sciences. Can planting submerged plants make the water clear and lead the reverse switches to plant dominance in eutrophic Lake Taihu? The answer is less possible, because there is competition between phytoplankton and submerged plants. Whether the submerged plants can grow in waters is dependent on the light availability. Phytoplankton has strong shading effects on plants in eutrophic lakes, and thus decreases the plants' competitive abilities. Alternatively, the Cladocera may be disappeared or reduced in numbers for the phytoplankton to gain advantage. Top\|down effects are likely to be more important in shallow lakes. Therefore, fish's predatory control on zooplankton is higher in shallow lakes, resulting in less possibility of grazer control of algae by the Cladocera. Under such condition, the colonization of submerged plants is less possible. If the plants are further damaged or meet bad weather, they may be suddenly loss together. Hence, the survival rate of submerged plants is very low in eutrophic lakes. All these correspond to the Alternative Stable States Concept of shallow lakes.