I ahve read everything I could find in this forum about wetland filters but I still have a few questions. How do you build a platform around the smaller container and how is it secured? Do you secure the screen to the platform or to the containers? Does the smaller container have to be shorter than the larger one or could they be the same height? I am also not exactly sure how to plant the plants.Finally, where do you get lava rocks. Sorry for all of the questions but if I am going to try this I want to make sure I do it right. Thanks.