You will get varying opinions on that but IMO, it's not worth hooking up UV because only pathogens going through the unit are going to be killed off (assuming correct flow) and those not going through will continue to propagate so you won't decimate the populations.
Also, if you like zooplankton to feed corals if you put any in the tank, then you will kill of the beneficial zooplankton.
Last comment is about your remark "seahorse/pipefish tank".
This combination is not very successful in the seahorse hobby, possibly because almost all the pipefish are wild caught and introduce pathogens that can wipe out the seahorses.
I wouldn't put anything in the tank except one species of seahorse all from the same breeding source, at least for a year until you are sure you have a handle on things.
The great majority of seahorses sold today don't make it a year before they die. (for a variety of reasons)