No more damage to the water than any other decaying matter in a pond. Other than sanitation/odor, the main reason USUALLY for removing dead tilapia would to prevent the nutrients they've removed from being available to problem plants/FA again. Tilapia raised as a food fish would not be for plant control or as a forage.
MRHELLO, there are a couple good studies by the food fish industry on LMB/Tilapia and CC/tilapia polyculture.
