Well I'm a super noobie at the DWC so right now I'm using ten inch airstones from the pet store (also available at Walmart pet section)
but I may change depending on how these do. I've used airstones in my fishtanks for YEARS so have some experience with the fish ones but have never tried any of the airstones or diffusers made for hydro applications.....AS YET anyway. I plan to be using a partial DWC setup for flowering for all my plants in the future as well so if I find something I like better I'll let you know.