It might not have been obvious in what Janet said, but the key to successful pool chemistry is

1. Testing what you need to, accurately enough to give you the information you need. (see Testkit info page)
2. Chlorinating consistently, according to your chlorine needs and CYA level (see Best Guess Chart page)
3. Adjusting other chemicals as needed. (ask, here)
4. Avoiding the use of anything you DON'T really need.
5. Circulating and filtering sufficiently.

Various types of feeders -- including both SWCGs and chlorine packs like you have -- help with #2, above. That's a good thing, but that's all they do.