Sweet done that system before and your Pryor one its all fun.....
my advice would be;
one lower temp and remove res from light so it dont grow,
cover tops of bucket system also,
but first take top 2in of rocks and clean,
with Styrofoam plate (throw away no paper style) make slit hole in center for support and lay on top of ring may take a couple time to get right then get white poly and do same covering outwards another foot make slits on side and drape to cover.hope it helps, they make rockwool covers now days when i use to lay out poly and cut slits for plant and waterlines.

an ounce of prevention is a pound of cure.......