I ran one when getting rid of a dino problem and it seemed to help. Its not something I would add randomly without having a purpose for running it but many folks seem to like running one.
What size tank? My view on UV sterilizers is they work the best when it’s apart of a loop. Water from tank into filter and return pump into UV back into main tank. That way no water gets around the UV filter. Also AquaUltraviolet is the brand I prefer.