Hey man, you absolutely can do both. Otherwise they would NEVER be used in fish ponds where the survival of every fish depends completely on a functioning biofilter!
There is no point to do both though because once youve got BB the UV is completely redundant. I am making a habit of repeating myself alot recently! Remember they grow ON the biofilter you introduce, on your roots, on he sides of ur res etc. ON Everything. Once we get them on the roots we are LARFING!
Please explain how sterilizing the water with UV, which kills the algae, will not kill the subtillis and any other benes that are introduced. And what or who is "they"? You seem to love to make vague assertions with absolutely nothing to back it up with. This thread is littered with it. Details, links, anything?