Interesting. I had a UV a few years ago, and it really didn't do squat (might have been from Aqueon, not certain). Personally, I hesitate with SunSun products, as they have no support in the US. I do, however, use one of their powerheads as additional in-tank filtration, aeration, and water movement, and it works really well (though you can only buy the replacement sponges on AliExpress (I had no issues with my order from AE, fortunately, just a long shipping time).