Ordinary Table Salt will kill the Slime in the Condensate Pump. We used to put Rock Salt Down the Condensate Floor Drains at work to keep them clear. BTW, I Do Not Recommend Rock Salt in the Condensate Pump, it may jam the Pump up. The Manufacture of my Submersible Aquarium Pump, told me to never use Vinegar on the Pumps, it weakens the Plastic, and eats at the Ceramic. To use Food Grade Citric Acid, at two to four times the Food Prep Strength.
Also during the Winter, I put a Tablespoon of Salt in my Rain Gauge, after emptying, keeps it from freezing, and cracking.