What are the pro's to this in a saltwater environment? Just browsing some online content and it seems that in most cases people lean towards not recommending it's use as it pulls beneficial organisms from the tank environment.
Ok. Here's brass tacks. It doesn't "pull" any beneficial organisms out of your system. It hammers the cell membrane of anything that passes through it provided the flow rate is at the right level. (Think of nuking a sponge in the microwave or getting a fatal sunburn) Will it kill some beneficial bacteria that are free floating in your water column, yes; however, this is such a small percentage, it is almost inconsequential as almost all of your beneficial bacteria are in mixed slime layers in your sand and bound on or within your live rock. The UV will also help "uphill" redox reactions that are usually endothermic as the wavelength of light hits with so much available energy. The flow rate is key in any UV application as the prok or euk must be in the radiation long enough to denature the cell wall or membrane depending on organism. I use canisters to pre-filter my UVs to clarify the water and allow more radiation to pass through the water flowing through my UV. Hope this helps.
I would use a uv if they made one small enough. every hardware we use is a cheat to what nature does, so I dont feel bad in cheat burning algae, cyano, diatoms, anything with a water transient phase. since we feed our reefs, plankton zapping doesn't matter. out of sight out of mind lol.
I run my uv 24/7 on my reef tank. Lots of fish lots of SPS and corals and I like to keep both healthy. I personally believe the emphasis people put on UV killing good bacteria is way overstated. Everyone tries to talk you out of a UV steralizer but since I started running one I have seen nothing but improvements and peace of mind with my Tangs.