you can dip it in freshwater to kill the pods on it, but leave the algae growth you have for now to help build more.
The purpose of cleaning it every week is if you go much beyond that the zillions of little spec pods will start eating holes in your algae which isn't helping anything. and then those pods end up back in the tanka dn you havn't exported any of the nutrients out of the tank, plus it won't be as efficient without the algae they ate off of the screen.
That's the purpose of rinsing in fresh water, not necessarily cleaning it. By lightly cleaning it, you are also pre-selecting certain species and types of algae, as well. That's up to you, though, and everyone's mileage may vary. I cleaned mine weekly from the start and I got to the point where razor blades and hard-bristled scrub brushes wouldn't even faze the algae growing on the screen.