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?
Woke up this morning to see my first romaine seedlings starting to emerge: