I'm sorry, I have 2 more questions. After having trouble keeping the bleach to register on test kit I went to the local pool store and they gave me a granular stabilized chlorinator for pools and spas, it says Sodium Dichloro-s-Triazinetrione....100%, provides 56% available chlorine. I asked if it contained any copper and he emphatically said no. Finally my chlorine level is registering good and holding well. I have noticed the past few days the ph level has gradually going down and is now reading 7.2, is that when I add Borax? How much do I add?

I have noticed when I take a reading the chlorine gets darker after it sits a few minutes, why would it darken? Are you supposed to read immediately and empty? or wait a few minutes? The test kit does not say much.