I have seen a Youtube of degraded trays when the UV was run 24/7. I've heard others say that the water moves past the UV light so fast that it's really not effective. I can't say for certain on either. I have only been using the UV light for 2 hours following water changes - I simply set a timer on my phone. I don't think it's going to kill pathogens but may have some positive effect on water clarification.
I don't know about bio-home ultimate. Richard, the Pond Guru swears by it but he's involved in selling the product. I tried culturing anaerobic bacteria to convert nitrates into nitrogen gas with Seachem Matrix and De*Nitrate...I was not successful. I think it can be done, but requires deep crevices or pores and very slow water flow. I'm currently experimenting with anoxic biocenosis clarification filtration (google Dr. Kevin Novak phD). But more time is required before I can comment on results.
Biohome, MarinePure's Cermedia, and Sechem Matrix/De*Nitrate are all 'contenders' in the claim for lowering nitrates with bio-media.
Actually, I think fast growing floating plants are better at indirectly lowering nitrates as they out compete BB in converting ammonia into plant tissue that is eventually removed by trimming.
Investing in ways to make routine partial water changes faster/easier is a much better investment than commercial bio-medias that promise lower nitrates. Nothing makes fresh water fresher than the partial water change of sufficient volume to reduce pollution.