Eastland, the cows haven't been gone long but they have always been on the place and the water has never muddied. Nor has it ever been weed free until this year. Thats why I credit the grass carp with both activities. I guess bullheads could be possible but they would have to have come this year. I've never seen any indication of them before and I've fished the water since it was new 4 years ago. Doesn't seem like bullheads could have made this type of quick impact.