In my previous home I found the racoons to be fearless, patient, intelligent, and strong. They tore up or found a way around every barrier I put up. I had the very same 35 gallon free standing pond on my back deck, and they'd scoop the fish out every time. They didn't totally destroy the pond, thankfully, but they did tear up the waterlily leaves. I used feeder goldfish, so there were fewer of them and easier to catch, I think.
The only thing I ever came up with was locking the whole thing up in a metal cage (like a dog kennel). I used to keep a high pressure hose/nozzle by the sliding back door and ease the door open to shoot them with it. It was the only thing that consistently drove them away. We were talking about putting in electric fences with photosensitive switches (coming on when the sun went down and the racoons came out) for the gardens when we moved away.
I do not miss the racoons.
