Thanks for all the suggestions and info. Our backyard has a 6’ fence and all of our neighbors are fenced so no uninvited visitors. In addition, the rules for entry are pretty stiff with my wife holding the top enforcement job. The kids range from 4-18 and all of their parents are aware of the rules. The 18 year group are ones who previously or currently mow and take care of our yard when we are away. So far, no one has feed the fish including us. The fish have been gorging on pond stuff and seem quite content. They seem to find something on the bottom of the water lilies that makes seeing them even in the murky green possible.