Yes. But depending upon what you're growing, you can get other problems from the leaves being wet if they do not dry out quickly. Tomatoes, for example, get fungal disease problems from being wet. Most plants can grow mold at the least.

Algae comes from light hitting nutrients. With enough aluminum foil, you should be able to stop that from happening. Any algae is bad, because they consume your nutes and can affect oxygen levels in the solution.

Bacteria is another thing entirely. They are like "the force" from Star Wars, half good and half bad. The UV device would be like the Death Star for your reservoir. It would kill almost everything, good or bad. Plants are happiest when there are more beneficial good guys than anaerobic bad guys. At that point, the UV does not help you. But if your environment is the opposite, killing everything is going to help.

So the UV is a good treatment for a specific problem, but you'd be better off not having that problem in the first place.