Building a viv with a waterfall is driving me nutz. I have the tube running up (behind) the foam background and have carved a stream bed down the front. But the water flow has a mind of its own and it runs into some plant cavities that I carved in the foam. Is there a way to plan ahead so the water goes where I want it to? I am determined to use this D*MN foam background I made. I had the same problem outside with the small pond where I used slate, flat rocks for the waterfall.