I think you guys are going to be excited with this update - I know I am
I've gotten a lot of the hardscape finished. As I mentioned earlier, the plan for this paludarium is to have the entire lower portion of the tank filled with water with no defined "land" area. So my goal with the hardscape was to create some three dimensional structure to provide planting areas and help visually fill the large open space in the top of the tank, while not taking up too much swimming room in the submerged portion. Based on this, I ruled out the traditional buttress design that most people use because it would take up a lot of space at the bottom, rather than the top. Instead, I tried to emulate "flying" buttress roots that would leave open space at the bottom.
Here's one of my sources of inspiration:
Like many builds, I began with a pile of foam. I used one 8'X4' sheet of 3/4" blue foam (Dow, from Lowes) and one sheet of 2" pink foam (Owens Corning, from HD). The blue stuff is a little denser, but both are easily carvable.
Here's a rough mockup of my "tree". I cut out the rough shapes using a kitchen knife and glued them together with a mix of silicone and Titebond glue (whatever I had on hand at the time). I also stuck in some cocktail skewers as additional fasteners. As you can see, I used many layers of foam to allow me to create nice depth.
Now for the messy part! I used a keyhole saw, rasp and file to shape the foam. Good thing my wife was out of town that weekend
After I had shaped the foam to my liking I attached it to the tank. I know a lot of people prefer to finish the background outside the tank and then attach it, but since mine was composed of multiple parts I thought it would be easier to stick them in first. It would probably have been easier to do the painting outside the tank, but it wasn't too bad (it helps that my tank is large enough for me to fit inside easily. Here's the left side siliconed into the tank. I used a full tube of silicone.
Another root added. I glued this to the tank bottom and to the first piece with Gorilla glue and added a bunch more skewers for additional structural support. The rope at the bottom was serving as a ghetto clamp.
Then I used GS foam to help hide the seams and add more structure. I also added GS around the bottom to hopefully provide better adherence to the bottom.
After carving down the GS, here's an overall shot of the background.