Trichlor tablets add chlorine, add CYA, and lower PH. Adding CYA is great when your CYA level is low, and can be a serious problem when CYA is already high. Likewise, lowering PH is great if your PH is high, and quite annoying when PH is low. As long as you are aware of what your levels are and either need or can compensate of the other effects, there is no problem using trichlor tablets. For most people most of the time, CYA eventually gets too high and you have problems.