The gravel is up to you, but I found it hard to clean my 5 gallon divided with it in there. Even a very small gravel vac wouldn't fit into the divided sections too well. I changed it out for large river rock from a craft store. It looks great and is easy to stick a turkey baster down in between for quick clean ups. I've also gone with bare bottomed tanks before, but found that I was constantly cleaning something unsightly looking up off the bottom. If it gets the least dirty, it looks very unappealing.