They prefer algae 36. For - Controlling Weeds 31. Mechanical weed control can be effective against emergent weeds such as cattails and some submerged weeds and should be started early and repeated to eliminate the food supply in the underground tuber causing it to die. A minimum water depth of 3 feet will prevent rapid establishment of aquatic vegetation. Maintenance of a level of fertility high enough to foster plankton population will cloud the water and prevent light penetration necessary for submerged weed growth.
Filamentous algae is the least desirable food of amurs.
Other aquatic plants will likely be eaten first. Amurs represent a biological control option that may reduce the need to use aquatic herbicides. Inert dyes reduce light penetration and thereby controls filamentous algaes and submerged weeds. They are usually blue in color and are not effective in water less than 2 feet deep.