Is flocculant harmful in the pool and when can I go into the water?

Depends on the flocculant:

flocculating agent in liquid form is placed directly into the pool water. When the pump is switched on, the flocculant can be distributed uniformly. After waiting time of about 5 hours the pool is ready for use again.

Granules On the other hand, it must be dissolved in a water bucket before use. When the pump is running, it is then slowly tilted into the pool, where it gradually spreads and unfolds its effect. A waiting period of 5 hours to be observed.

Tablets in turn, the best dosing floats in which they dissolve slowly and give their effect to the pool water. Because the active compounds in tablets only gradually dissolve and the concentration is very low, the pool can also be used during the use of flocking agents in tablet form.

http://www.poolzubehoer.de/general/the correct application of flockmittel-im-pool.htm

You can use Flock tablets or cartridges immediately enjoy a refreshment in the cool pool water.

Come on liquid flocculant for use, a few hours pass where additional pool pump is used, to be able to bathe again safely.

https://plitschnass.de/flockmittel-Application/#Wann_darf_man_nach_der_Application_von_Flockmittel_wieder_im_Pool_baden