Crystal Blue 137 Tsunami DQ Aquatic Herbicide-37.3 Percent Diquat Dibromide-1 Quart, 32 oz Diquat formula kills surface and submerged weeds that are copper resistant Effective in controlling hard to kill weeds like duckweed Consists of 37.3% diquat dibromide 2-8 quarts per surface acre depending on infestation & type of weed for aquatics Use Plex Mate to enhance effects when treating floating marginal weeds