#1 Remove and save water.
#2 Remove fish and store in tanks cover if needed.
Carefully net fish.
#3 Pressure wash debris off rocks, always put clean out pump in lowest spot of pond.
Be sure to have enough help, it's a dirty job.
Larger ponds will take more time.
#4 Refill pond when done; make sure to add beneficial bacteria, fish, start feature running as soon as possible.