I'm using an oval stock stank as a garden pond, roughly 3 feet wide and 5 feet long. I have the top open currently. I have a marginal plant on a pretty solid base. Two nights in a row the marginal plant and base were completely knocked over by (I'm guessing a raccoon or a neighborhood cat) so I think it's time for a protective covering over the top so I don't lose my fish. What would be best? Perhaps a rigid mesh so that the animal can't push through or get to the water?