Sorry mine is installed on one of the over flow lines (I have three) before it reaches the sump. It isn't ideal but it seems to work just fine. I think the recommended installation is on the return as the last stage.
the ones i was looking at had a much slower flow rate than my return thats why i was thinking about putting it in line with a media reactor that circulate in the sump
thats fine to do i have a big one that is rated for at the most 800gph for it to be good and effective it will work at a way higher gph max of 2800 i think it said but is not very effective. i have a 40w gamma uv