When a poolish is ready to use, it should be covered in small air bubbles and risen slightly. Be careful not to over ferment your poolish, however, as it can grow out of control quite quickly and go bad. The best way to use poolish is by letting it rest at room temperature for about 1 hour to begin the fermentation process then placing it in the refrigerator for 16-24 hours, or overnight. The cold temperatures of the refrigerator will allow the poolish to continue fermenting but at a much slower pace, leading to a better flavor profile and texture when used in a pizza dough.