You don't clean gravel in a well planted tank. You just prun the plants and remove any large loose or dead leaves. All the stuff that gets into your gravel will break donw and evertually be used by the plants. That said I've heard on people acually putting dead leaves under the substrate to provide plants with more nutrients. You will have gunk build up, its called mulm and its a inportant part in a planted tank. Don't be suprised if you pull up a plant and have a cloud of black stuff come out of the gravel, it will settle down again.