How many pucks to get to 30 to 50 ppm cya

[waterbear]

You might actually find it's less expensive and easier to just buy CYA (conditioner or stabilizer) and add the required amount to your skimmer and then use bleach to chlorinate.

[Poconos]

If you go the puck route then be careful of the contents. Anything that says multi-purpose probably has copper or some other undesirable ingredient. Check the label because I've seen buckets of the stuff at Sam's Club that looked identical according to the ingredient label but one kind was more expensive and said multi something on the bucket. As I recall the clorine concentration was also lower for the multi-purpose stuff.
Al