I would just throw them away. They are very inefficient as aquarium knowledge has advanced. And it's not hard to see why. Look at the bioballs that you have and see all the air inbetween the posts on it. That's all wasted space that has no room for anything to grow to help your nitrogenous wastes. Other than things that will impede overall flow. Ceramic media that is even 1/4 the size has the pores and ability to grow more BB than the bioball.
Throw away 300 bio balls? No. Use them. Bio balls are mainly used because they get the job done just as well as ceramic media and their surface area NEVER diminishes as ceramic media does. Bio balls can just be rinsed with a hose and their surface area is the same as day one. You could argue you can boil/pressure wash ceramic media but i assure you that its surface area decreases over time and may even drop lower than the surface area of a bio ball. From your point of view you can say a dense sponge has a similar surface area than ceramic media, Both will end up getting clogged and their surface area is diminished.