This is a koi pond question I know it's not the norm for this forum. My parents have a koi pond in their backyard it has four large koi 6-9# and probably twenty six to eight inch assorted goldfish. The yard is fenced but backs up to some open land. They have seen a gbh come around but run it off when seen. The pond is about three feet deep over the last few days all of the goldfish have disappeared no sign of fish remains or scales. I don't think the gbh could have caught all of them without being seen. The koi are fine it's not in a path that an otter would follow and by my experience they would have killed the larger fish. Too deep for raccoons to do any damage. Does anyone have an idea what else might be the cause