I'm doing a water change right now... It's raining.
Other than topping off evap. and water my dogs drink, I don't do any water changes. I do use my pond water to water my Hosta's in the summer, but maybe only 50-100 gals, per week. So really I guess that is a small water change, 5-8%. I just put the hose in the pond and grab a coldie to refill. No buckets. Why not use the pond water on the lawn and plants? They will love it.