I have a turbo twist 36 watt and keep it running 24 hours. Many people claim uv's don't do anything... I disagree. I think they definately keep the unwanted bacterial count down, and if nothing else they do control the spread of unwanted algae. They do not take ich off of your fish, but they will knock out ich that is free swimming which goes through them. you need to run water through the uv slowly though in order for it to work and change bulbs every now and then. I keep it on its own pump, which is just a powerhead hooked up to tubing that I then connect to the uv. My tank is always crystal clear. And my fish thus far are fine....(however I do have two cleaner shrimp, two fire shrimp which also clean, and two cleaner wrasses) I also qt my fish in hypo before adding them to the main tank which is a 200 gallon. I vacume 1x week and change 10% of the water q weekly as well. You can get a used uv because ultimately you will need to change bulbs anyway. check out the big online auction site. that's where I got mine for half the price and I have been running it without a bulb change now for 4 months...