How do you clean a pool if it has been neglected so long that the water is green and it has tadpoles living in it?

Pump out the pool. Pressure wash the pool interior, remove debris. Finish with an acid wash. Check all Plumbing for damage etc. Change out the sand in the sand filter (if fitted) Clean all skimmers and leaf filters at the pump and the pool. Fill pool and adjust it chemically after 24hours with pump running.