Yes, pet turtles can be kept in a pond as long as the pond is properly designed to meet the needs of the turtles. The pond should have a non-toxic liner, proper filtration system, and places for the turtles to bask and hide. It is important to also ensure that the pond is escape-proof and safe from predators. Additionally, the water quality and temperature should be monitored regularly to ensure the health of the turtles.