This is entirely up to you. We do not recommend closing the pool if there is a LOT of debris in it and in that case you should vacuum it all out, however, a few leaves and bugs are OK. Most people vacuum the pool right after they open it in the Spring anyway. If your area has a bad winter and part of your cover falls in the pool, you will just have to vacuum it again when you open it, so most people would rather just do it in the spring and only have to do it once.