Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants kill cattails

From Malone and Sons, who furnish a LOT of the Triploid Grass Carp in the U.S.

Grass carp prefer aquatic vegetation such as Duckweed, Chara, Naiad, Potamogeton, Eurasian Watermilfoil, Bladderwort, Hydrilla, Elodea, Coontail, Spikerush and Water Stargrass. Grass carp generally do not prefer filamentous algaes, watermeal, watersheild, spatterdock, waterlilly, arrowhead, water hyacinth and cattails. Plant preference is greatly linked to fish size. Smaller grass carp will readily eat filamentous algae and pithophora while larger grass carp do not prefer this species but will eventually eat it once they have eaten other available species. Emergent vegetation such as hyacinth and arrowhead are generally not preferred by grass carp, however once grass carp have reached large sizes they will eat these species.

But, for specific algae control, I'd use Tilapia instead of GC. Check with Mi. I don't know if GC are legal to stock in Mi. I know Tilapia are legal.