Well, I passed on the 'opening kit' that the pool store always has for sale (1 kg oxidizer, 1 litre stain and scale remover, 1 litre 40% algaecide) and used chlorine only (liquid). Quite happy with the results. All that's left is to add some salt and wait for the water to warm up so I can turn the chlorinator on. Solar heat raised the pool from 45f to 55f today. Yay!