The issue with changing the sand at this point is we've yet to get a true OCLT result reported yet. IF the OP started at a 15FC level last night and dropped to 8FC today it shows a good bit of Baqua still hiding somewhere (ladders, skimmer, Lights). You want as much of this Baqua-Goo converted before changing the sand. If the OP were to change the sand now, and there was a large amount of Baqua-Goo still in the water, the new sand could be contaminated before the conversion was complete. A good OCLT will hint to where the Baqua levels truly are.
The reason we suggest no CYA to be added during the conversion is that you want as much of the chlorine to remain active to convert the Baqua as possible. At the beginning of the conversion the process consumes the chlorine much faster than does the sun. Towards the end however you can get away with adding only at night to save a few bucks.
The reason we suggest no CYA to be added during the conversion is that you want as much of the chlorine to remain active to convert the Baqua as possible. At the beginning of the conversion the process consumes the chlorine much faster than does the sun. Towards the end however you can get away with adding only at night to save a few bucks.