One of my cannisters has a built in UV but I'm not going to use it because I am keeping ceramic media in both cannisters. This cannister (700gph) was not designed for media so the UV is sitting right where I added the media...that ain't going to work.
However after a lot of reading and researching I am adding an inline UV on the intake of my second cannister (500gph), this cannister also has media but I can't see how a UV on the intake would harm the bacteria.
At least that's today's line of thought
MeCasa