treating some today. difficult without chemicals, grass carp do not like it. If you decide to try chemical, most economical is aquatic glyphosate 2% solution, and 1% of 2,4-d liquid and surfactant. It may requie 2-3 appliaitons but will slowly reduce abundance. We used to use and recommend 2,4-D granular (navigate, aquakleen) but has gooten so expensive.

Greg Grimes
www.lakework.com