I have an 18x18x24 exo terra cage and I want to incorporate a small waterfall and tiny river into my habitat. I'm obtaining a MHD and they require moving water to drink from. I'd like to have an external pump that I can keep outside my habitat and use tubing to deliver and pull water. I'd like the pump to have a filter on it to always be putting fresh or fresher water into the habitat than is pulling out. I'm looking for not only pump/filter ideas, but also ideas on how I set up the waterfall/river in the base of the habitat. I'd want to keep the water in the waterfall and river only as I have a monsoon system to keep the substrate and everything else wet. Any links to websites where I can purchase ready made kits or links to custom how-to's would help greatly. Please let me know if you have your own ideas as well. Remember, I only have 18x18 at the base to work with, maybe a little less with the foam rock background that I have.