This is all helpful- thanks! I'll get a test kit online. I'm using WaterTrend Sani-Chlor and Spa Shock. On my aqua check strips the TA is 80 and the PH was 7.2 last night and is 8.4 this afternoon. This morning I added a weekly spa refresher, scum destroyer, and some Unique. I do have sponges in the tub.