Karen Walk wrote:How big and deep do you want your pond?
I dug a 30'-40' diameter pond with a full size backhoe in heavy clay. It is 8' deep at the deepest. I used the front bucket and the backhoe attachment. It was a total pain in the ass. Digging and moving soil with a wheeled vehicle makes much more of a mess than a tracked vehicle, so you need to take into account extra cleanup time.
Tractor buckets are generally lighter weight metal and have lower carrying capacity than backhoe buckets. It is easy to over-load them (I have used tractors with buckets and never would have been able to dig my pond with one).
You should look into rental costs for a small excavator.