I'm somewhat at a loss. Part of me says your water is clean from a chemical standpoint (CCs<0.5 ppm and OCL ~ 0ppm) and so you no longer need to maintain shock level FC but I'm not sure why your clarity is so far off even after adding cellulose fiber to the sand filter. I've only ever heard of using DE in a sand filter, not cellulose fiber. Therefore I'm suspect of cellulose until someone confirms that it is equally as good as DE in a sand filter.
I'd like to know if your particulates stay suspended or sink. You could shutoff circulation overnight (maintain your FC) and see what happens. Perhaps if the stuff settled out, then you could vacuum to waste to get rid of it.
If the stuff stays suspended, then I'd have to defer to the senior experts here who know if a clarifier will work for your situation.
Sorry, wish I could be more definitive.
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