last phase of slam, overnight vs daytime

[Oscar7]

Raised fc level to mustard algae shock level as water is crystal clear and no cc, with cya @ 55 raised to 36. Little more than necessary, but emptied the carboy.

OCLT: tested 36 at 2 am, 36 at 10 am. No cc.

10 am to 3 am (long work day ): 36 fc, 0 cc dropped to 22 fc, 1 cc.

Does the sunlight consumption of chlorine produce cc? I almost never register cc when drop testing. OCLT to me shows slam complete, but daytime cc is interesting, perhaps because i gave a good brushing around 11 am, exposed more organics?

 

[duraleigh]

CC's can and will vary throughout the swim season, day and night sometimes even. They are an indicator but not proof positive that you need to do something.

The 14 ppm drop in your FC is probably a better indicator and combined with the CC's tells me your SLAM is not yet complete.

I would continue the SLAM for at least 24 more hours until your FC consumption stays down.

Of coursem we would like to see your OCLT done between early dark and daylioght or as close as possible. I cannot understand why you passed that OCLT based on your other values but I would ignore it and go back to your SLAM values.