Before I set my 40B up, I would have said no unconditionally.
But I have to run one on it (for now anyways) to keep the water from going brown. I fought the cloudy water for a couple months before I tried a UV. It cleared my water up in three days. I pulled it off a month ago, and started to see the cloudy water return. So I put one back on.
It is the first time I've ever had to run one. I'm hoping to pull it off in a month and see how the tank does, as I feel like they shouldn't be ran constantly, but only when needed.