gcaver

I am a chemist who just bought a spa a month ago, so I have had an absolute ball leaning the ropes of spa water care. I have done a ton of reading on the forum here and other resources - love it! Quick question: I spiked my Br up to around 10-15ppm yesterday with sodium bromide (yes, purposefully) because I wanted to do a little experimenting with how long it takes for levels to fall in my tub. I planned on doing a full water change soon anyways. I confirmed with strips that I had hit my target then walked away for the night. This morning, to my absolute amazement, my Br levels were gone (1ppm at best). So I repeated the spiking again to 10-15ppm. Checked it 2-2.5 hours later and it's gone again! What the hell is going on here in my water?? FYI, I also have 3 Br tabs in my filter basket (I know it's not ideal, floater has been ordered). My spa is covered all the time, is never in sunlight (under a porch overhang), and is only used at night; so it's not breakdown from the sun. The ONLY thing I can think of is that I need to shock with Cl in addition to the Br loading so that the Cl can oxidize and "activate" the Br...??? Is that my problem? Any and all help would be greatly appreciated!!