spa guard is the brand name, on purple bottles?
the tub has gotten ALOT of use since being set up, was already sudsing a bit due to some guests with residual laundry soap, and the chlorine tab this morning didnt help. even after 10 ozs of shock and 6 ozs sanitizer, the water was still murky and had an odd smell to it. oh well, its been almost 3 months. time for a water change i guess....