Don't put liquid chlorine in with the pucks.

16lbs of pure trichlor in 20,000 gallons should give you about 50 ppm CYA after using it all up. When you say puck carrier do you mean a chlorinator that's plumbed in or a floater?

As PoolDoc said, starting up with the trichlor should work pretty well for you especially in a feeder. If it takes a day to fill, add bleach (or liquid chlorine) and mix it with a brush so it doesn't go green while filling.

- Sorry PD, I think I was posting at the same time as you - Dave -