One of the best ways to protect a hot tub cover from the sun is to use a spa cap. This is an inexpensive cover that is placed over the cover, and can be removed with ease. These are usually sold in standard sizes, and they cover the entire spa, including the lifter bar. They work like a traditional shower cap, but with an elastic band around the bottom to hold them on. You can use one on one side of your tub, or on both sides.
Another method to protect your hot tub cover from the sun is to clean it regularly with microfiber cloths or soft rags. Using UV protectant spray can also help keep your cover from cracking or drying out. You should also check the cover for any small rips or tears. This could expose the inner foam, allowing water to soak in. Water-logged covers can support the growth of mold and bacteria.
The best way to clean a hot tub cover is to avoid cleaning it with an abrasive solution. Use a mild liquid dish soap to wash it, and a soft bristle brush to scrub it off. Make sure to hose it off afterward and towel dry the cover.