How does my fish tank sound? (10 very easy pionts)?

It's just a little overcrowded. If you are doing water changes often enough you should be okay. You should be attention to ammonia. More fish...more ammonia. The kind of gravel you have doesn't matter. Just put in whatever is to your liking. My 29 gallon tank has rocks that I picked from my backyard in it instead of store bought gravel. Your food is fine, just don't over feed, that will cause issues for the water condition as well. As for your filter, like I said, you'll need to do water changes. Type of filter won't really matter. Good luck.