I didn't mean to make it sound so mysterious, but there are a few too many coincidences for me, all of this happened within a week or so. The herons are probably the easiest to explain, they don't normally feed in ponds around here, so when they first came and there was abundant food they came often. After the barramundi grew a little, the food at the surface dried up and they went back to their normal take out joints. Some of the turtles and all of the crabs, migrated into the pond so maybe they just migrated out, the snake is the hardest to figure, but maybe like the heron, he is a sight hunter. My water visibilty is 3" and with the fish gone or in hiding there was not much for him to eat. I am just starting into my second year with the pond, so maybe it's all part of a cycle and by next year I will have a better understanding....or not.
