Thanks for the response, Grace. Things are looking up, I have been relentless in the testing and shocking, using only 6% bleach. Today the water is Mt Dew green but clearing - I can see the bottom. Also the filter seems to be flowing better. I would highly advise anyone doing this with a DE filter to change the medium at least once during conversion. DE is cheap and it does capture a lot of gunk. I have been careful not to add too much bleach at once to avoid any negative consequences, been through 14 gallons and I figure will need about 6 - 8 more to complete the job.
Question: Once things clear up, to get rid of the CC will I need to shock to whatever the CC level is? e.g. Baquacil is gone, cl holding at say...2. but CC is 15, I assume I would need to shock to 15? For how long? Only then will I add CYA to stabilize...and replace DE once more.