That's so the algae doesn't grow in the white and orange buckets and it keeps the solution in the blue buckets cool in the sun. I don't need them on the blue buckets since I put up a shade cloth. I got lazy with the orange wicking buckets and haven't covered the sides yet. I will use black plastic or black weed fabric to cover the orange, so algae doesn't grow.PS, why do you have the reflective covering over the buckets?