I have not used shock in the pool since the 14th. It does have calcium in it. I guess I don't know what the calcium level is. I have the CH 5 PH 7.5 on the reading this AM. I put in 26.5 oz of acid since the 26th and the pool is finally clear today!!! I have not added any CH for the last week or so. I did need to add a second filter pump because the SWAG would keep showing low flow and it made it thru the last running without turning off!!! I am really just playing hit and miss on the pool stuff. It is a good thing that my kids are loving the pool for the time I have in it.