Submerged terrestrial grass along inundated shoreline will initially for month or two provide some shelter for the GS. However what cover will they have for continued dense refuge and survival as the grass quickly decomposes? Grass shrimp are a great addition however dense habitat needs to be present for the population to thrive year to year. IMO most pond owners really don't understand the full concept of proper sport fish habitat. Ideally grass shrimp should be raised in their own small forage pond with minnows and then moved to the main grow out pond.
