garden ponds in general

I had a raised pond built by my garage it started small but the fish grew so I had to make it a lot bigger, it was 12’ long 3’ wide and 4’ deep.
It was easier to maintain and the kids could see the fish better, I still had herons but never needed a net we even gained 2 bream from somewhere,
I had the odd goldfish and 20 koi, my biggest fish was my sturgeon 18” long and as tough as nuts. He found a flaw with a raised pond as he escaped 3 times, the 3rd was unlucky as it was 2 weeks later we found his skeleton and skin, he had leaped up and landed behind the filter out of sight.
Now I have a bigger garden but no pond and I’d never keep the dog out.