If you have steep sides, the herons can only wade so far in. Unless you are raising prize winning show fish, I wouldn't worry about it. Enjoy them for what they are.
I have a good heron story....
Our town zoo has a pond that is about 3' deep. There is a raised deck over one end of it, about 10' above the water. There is a concrete wall along the pond edge, going under the walkway. There are fish feeders on the deck, and for a quarter, you get a handful of fish food. The pond was full of carp. My daughter and I saw a heron fly up and land on the wall under the deck. So, I bought a handful of fish food, walked over to just above the heron and threw in a couple pieces. The carp started coming over. So I threw in the whold handful.... the water starts boiling with fish, the heron goes nuts and spears an 18" carp right through the middle. My daughter is shocked but cannot turn away. As the heron attempts to lift the carp out of the water, it loses its footing and falls head first into the boiling fish mass, and completely disappears! My daughter yells, "You killed the heron!" I am standing there with my mouth hanging open for what seemed like 20 seconds or so, and then the dead carp with heron beak comes up out of the water and the bird manages to flap up onto the wall with its prize. It drops the carp in the rocks behind the wall and the carp starts flipping and flopping back towards the water. So the Heron grabs it and flings it away from the water, but the carp keeps heading back. At that point, we moved to get a better look. That's when we saw the heron pick up the carp and fling it against a cement retaining wall about 4' off the ground. Blood sprays out of the carp across the wall with loud THWAPPP! The fish keeps flopping and the heron keeps flinging it against the wall. YIKES!!! By now its a bloody mess worthy of a drive-in slasher film down there. My daughter and I wince each time the heron beats the carp against the wall. After about 10 smacks on the wall the heron starts spearing the carp over and over and it finally stops moving. Then it took the carp by the head and started trying to swallow it. I'm telling you, that fish looked like a Folger's coffee can going down a garden hose. For about five minutes, the tail is sticking out of the heron's mouth, its hoping around with its beak pointed at the sky trying to choke it down and my daughter is yelling at me again that I killed the heron. Finally, after about 10 minutes of this, the heron gets the fish all the way down, walks over to the pond, drinks some water and just stands there looking like your uncle after his third course on Thanksgiving! I would have never thought that bird would have even tried to catch a fish that large, let alone be able to swallow it. It was truly amazing. My kids and I still talk about it each time we go to that zoo and walk on that deck.
