I used to have a good sized (10' x 20') pond with koi... never had a problem with coons, but once the blue heron discovered it...
he was beautiful... but once you see him eating koi and goldfish over a foot long you have grown and had breed for years... I could think of alot of names for him.
Now I will only keep pretty goldfish, at least they are cheaper and breed easier. I have also found that with hatching several lots of goldfish eggs and growing the babies inside (to increase survivability) that waters oxygen content and temperature (colder) can greatly increase growth rate.
My new pond is only about 8'x12'. Its not done yet. I really originally put my ponds in for the dogs... the fish are on their own. But since the dogs never got the fish, the heron was a bit much... especially when the fish are 6 and 8 years old.
"Pedigree indicates what the animal should be;
Conformation indicates what the animal appears to be;
But, Performance indicates what the animal actually is."
- author unknown