i also know that PPG makes a cal hypo tab. these tabs are 65-68% active. they sell them for use in PPG feeders, so i don't know if they are OK to use in floating feeders/skimmers. their pH should be much higher than a trichlor tab, though so it seems that it would be safer to use in a skimmer than a trichlor tab.

PPG tabs are also probably not available through walmart or home depot

j