Unless you are hung up on the idea of absolutely fishing there, which sorry to say from my point of view, it looks too small to fish in, I'd just use the pond for minnows. You could raise more fathead minnows than the herons could ever eat, plus you can feed them and enjoy watching them grow. If they got quite plentiful you could buy a couple channel cats to help keep the numbers down, or just let them multiply maybe sell bait? Maybe others can comment.
If you drain it dry your sunfish won't survive the renovation process.
