I dont think algae can harm your plants.
Each time i had a algae problem with a nepenthes, or any other plant, i resolve the problem by reducing the watering. Anyway, i always had better results when i grow my plants on the dry side.
All you need to do to get rid of algae is to just let it dry a bit. I had huge green sheets of gunk growing in my flytraps' tray, but when they dried out it was fine.