coralife turbo twist recommends that it is connected to a prefilter first. I have mine connected to my canister filter exhaust. The reason behind having it hooked up to a filter is to help prevent build up in the twist channel. I was getting a little green dust like algae on my front glass (next to a window, had no choice in placement) once I hooked up my UV and cleaned my glass again and did a water change again, my green dust on the glass is gone. I could not figure out why my glass was getting a hint of green dust on the front glass, the tank was next to the window not in front but it was and after reading about the UV I picked one up and now 6 weeks of using it, I have no problems and it really only took 48 hrs and my green dust was gone and has never come back. Some people will argue over the fact that it will kill other beneficial organisms in your tank like micro verts and phytoplankton and other stuff, but are you really trying to harvest and maintain those organisms? good luck if you are. I have copod and stuff on my rocks can see them crawling around they are not dead and after six weeks of uv sterilizing they show no signs of dying or not being able to breeding. The only problem with my copods are when I change my filters media out I have to watch I don’t dup the copods out, it maybe me I don’t know for sure but my copods love to live in the canister and seem like that’s a breeding ground. I have read and heard three different running times with a UV, some say 24/7 some say 6month and a few say run it for a month or as needed. I might only needed to my run to split my single celled algae. My parameters are all on target, silicate is 0 or none detectable, phosphate 0, ammonia 0, Ph is 8.3, trites 0 trates 0 CA 420 DKH 8.6 ALK 3.9 so on and so forth. Like I was saying I could never really say for sure why I was getting a green dust because my levels were always on target. Like I was saying the benefits out way the negatives, even if you were to run it for a couple of weeks to split any single cells or kill off any free floating ick in the tank. You should just make sure you are profiteering the water before entering the twist channels. Just my 2cents