how to start a pond with 2 baby koi?

[budgenator]

Would dogs keep them away and would they come into the city?

Depends on the dog, my Dachshund/Chihuahua mix probably wouldn't intimidate a heron for very long, the Beagle and Jack Russell mix might have to rescue Taco from the bird! We have herrons in the area but haven't had any come in the yard, but they've definitely looked hard. I think it's do to the three dogs. We had one blue herron, at the pond at the old house (in the city), but it wouldn't walk in the pond liner and left. The old house was within walking distance of lake Huron on the east, we had a canal from the lake to our local river on the south and the local river on the west, so the herron wasn't under presure to be at the pond, YMMV.