Hi,
Thank you all for your answers. I live up north in Quebec,Canada where we have temp in the winter of -30. The earth freeze sometimes up to 4 feet. So i would need a pond of 5 feet deep to have at least one feet of water that does not freeze.
The summer are quite short.
Well i did it i bought a common goldfish today in hope of building a pond next summer. I know they need 50 gallon of water each. I bought it now because it's a all white one which are rarer than the orange ones i see all the time. I've paid 0.66 cents + taxes for this fish. Also what kind of goldfish are the ones who are common complety white but are butterfly at the same time with blue spots here and there. Those are more expensive. They are not egg shaped they are like a common goldfish.
Simmillar to this