A shock dose kills what is in the water but does not remove it. Here is why the cloud lingers after shocking and how to clear it within a day or two.
Short answer: shocking deals with what is growing in the water, but it does not remove anything. The dead material becomes a haze of particles far too fine for your filter to catch on its own. Give the tub 24 hours of filtering, then add a clarifier, and the cloud should clear within a day or two.
A shock dose oxidises bacteria, algae and bather waste. That is essential work, but the leftovers stay suspended in the water as microscopic particles. Standard hot tub filters catch particles down to roughly 20 microns, and much of this debris is smaller, so it slips straight through and the water stays milky.
In other words, cloudy water immediately after a shock is often a sign the shock worked. The job now is removal.
Run the filtration for a full 24 hours after shocking, not just the usual daily cycles. Rinse the filter halfway through, because a loaded filter passes water without cleaning it.
Then add a clarifier. It binds the fine particles into clumps large enough for the filter to trap. One dose is normally enough; a second dose two or three days later finishes the job on a badly clouded tub.
Finally, retest with a strip. If pH or alkalinity is high, the water can also hold minerals in suspension that add to the haze, so bring the balance back into range while the filter works.
If the water is still cloudy four or five days after shocking, with a clean filter and balanced water, suspect the filter itself. A cartridge past its lifespan loses its ability to trap fine debris even when it looks clean. Filters typically want a deep clean monthly and replacement roughly yearly.
Persistent cloudiness that returns within hours of clearing can also point to a heavy residue load in the pipework, which a plumbing flush at the next water change will sort out.
If sanitiser is in range on a test strip and the cloudiness is just post-shock haze, a short soak is generally fine. If you cannot see the bottom of the tub, stay out until you can.
Not straight away. Back-to-back shocks add more oxidised debris to remove and can push your sanitiser far above the comfortable range. Filter and clarify first, retest, and only re-shock if the strip shows sanitiser demand is still high.
No. They do different jobs. Shock deals with contamination; clarifier helps the filter remove the leftovers. Cloudy tubs usually need both, in that order.