I wrote of screening gravel from a desert wash for use in containers > I have to screen mine, though, through > 1/4" / 10mm wire mesh." Alberto asked > And which size do you use? Most of the time I use what falls through this screen and return the larger pieces. This is really good for almost all cactus and succulents as-is, as well as for bulbs needing good drainage. If I am planting a large container that I will need to move from time to time, I may add a large quantity of perlite or pumice to make the container easier to move. But pumice is hard to get here now, since the one mine in Arizona was closed. For bulbs that I think need a more silt- or clay-like medium I use another screen after this, a large kitchen strainer that has a mesh size of 1 or 2mm, and use the fine material for those seeds. Generally when I read something comes from sandstone soils or need a well-drained mix I use the larger size; for something from shale soils or renosterveld, or something that is semi-aquatic, I would try and use the finer size. Leo Martin Phoenix Arizona USA