I think that both the Defeating Algae and the Shock Your Pool articles in the Pool School should explicitly mention that the preferred source of chlorine in these cases is chlorinating liquid or bleach, though Cal-Hypo may be used of the CH is low. Trichlor pucks/tabs should not be used as they are too slow to dissolve, are too acidic, and increase CYA. Dichlor should not be used either since it increases CYA by a large amount.