Does size matter? Is it better to have a bunch of smaller size or fewer larger size Bio-Balls?
Size is important as well as the design of the bio ball. There is a vast difference in the surface area from different manufacturers.  Our bio balls are covered in spines to create a huge surface area on each bio ball. Most other manufacturers have less surface area and try to use a sponge in the center of the ball to make up for this. The challenge with the sponge is you will need to take each bio ball apart to clean them as organic debris builds up.
We are releasing a 1 inch bio ball identical to our 1 ½ inch in the next few weeks. Yes, our 1 inch bio balls  can pack very tight, producing more surface area than our 1 ½ inch balls.