What I normally do if I need cya to rise, is to take a cya level reading, fill 1 plastic cup with CYA, dump the contents of the cup into a sock, tie the sock with both a tie and rubber band, put in skimmer in the morning just after pump starts, wait 3 days, remove sock (all the cya should have disolved), wait ~2 more days and read cya level, if still too low, repeat process until cya is where I want it. I'm not aware of any issues with leaving the sock in the skimmer....just make sure to have a sock that doesn't have any holes and keep in mind that at least for the first few hours - there will be at least a ~0.1 drop in pool pH for my size pool - but if done at the start of the day is normally easily corrected via airation by end of day. I wait for at least 1hr after putting sock in before letting anyone swim - although that is probably more a matter of personal preference. I don't run pump continuously for 24hrs after adding, only ~12hrs which is usually enough given our water temp is ~88 degrees most days and the skimmer gets good water flow.