UV filter placement

[MODreefer]

My Question revolves around plumbing. I'll preface this by saying I'm new to the hobby. I'm going to plumb two tanks into one system. One will be a 180gal predator tank the other a 120gal mixed reef tank. Where would I install the UV filter? And would it be plumbed back to the sump or continue to the DT? If plumbed to the DT, would it be plumbed to the reef tank, the predator tank, or both DT's? Thanks for everyone input.

[menglish]

If the two tanks are sharing a common sump, i would plumb it with the treated water going back to the DT