How much time should pass after the application of JBL PhosEx Pond Direct before the UVC water clarifier can be put back into operation?
There is no general answer to this question.
JBL PhosEx Pond Direct binds the soluted phosphates present by means of a chemical precipitation, which means a transformation into a non- (or under certain chemical conditions) water soluble form. How much time now has to pass before a UVC water clarifier is put again into operation strongly depends of the circulation rate, which means how long it needs till the whole water has passed the pond filter.
Furthermore the existing current / water movement in the pond and the way that JBL PhosEx Pond Direct is added has to be taken into consideration. The time period is shorter with an extensive distribution, i.e. with a (plastic) watering can and with a good water movement than with an addition concentrated in one spot in a garden pond with slow water movement.
Besides the distribution the water temperature is also relevant (though this only needs to be mentioned in passing here).
The switch-off period needs to be at least twice as long as it takes for the pond water volume to completely circulate. To be on the safe side with the phosphate precipitation a turn-off time period of 48 hours can be considered as being sufficient.