After being out of the hobby for 5 years, early this year my fiancee rejuvenated my interest in terrariums. We decided that we could fit exactly one terrarium in our tiny one bedroom apartment. 55 gallons (48"x13"x18") was the maximum that would fit in our living room, so I decided on that.
The ultimate goal of this terrarium is to be self sustaining. I have read extensively on this, and written on this goal here.
general-discussion/topic35619.html
I doubt the tank will be able to be completely self sustaining, but I hope to only have to add leaves and occasional kitchen scraps.
The overall design of the terrarium needs can only have the short end facing the wall covered in substrate, but must be transparent along the long axis. Initially I was going to add a water feature, but in reality that would eat up precious floorspace, which will be used to grow microfauna. Besides, I made a tank with a waterfall in it six years ago. The soil will be several experimental soils with different properties. Most of my plants will be grown epiphytically allowing an understory to develop, and they will be watered by an automated misting system. There will also be internal air movement, provided by a computer fan. This will all be sealed up, and hopefully only opened to prune plants and add leaves (any maybe remove offspring, if I'm lucky).
I scoured craigslist for a few weeks, and eventually found someone giving away a free 55 gallon. It came full of old aquarium stones and assorted crap, which I discarded, and wasn't in perfect condition. I washed it and washed it, but there was permanent (and I tried everything) hard water stains at the top, and various scratches, and the frame was warped/melted. So I sterilized it with bleach.
Next I drilled the holes. Having never drilled glass before, this was quite nerve racking. This was also a major reason why I didn't want to buy a new tank, as I feared impending doom. Luckily, there was no catastrophe and everything ended up working out. I drilled: one 1/2" hole in the bottom for drainage, two 1_3/8" holes for ventilation and two 1/2" holes ate the top for the misting system and temp probe. One word of advice when drilling with a hole saw. Use lots of water!
The next step was to smear black silicone across the back of the terrarium, to hide the Great Stuff that I would be adding later. I also used the silicone to seal up the tubes sticking out the back for drainage and misting.
I ended up using two layers of GE black silicone II. It took one entire tube to cover the background and the false bottom. I didn't use gloves, and my fingernails looked pretty nasty for a couple of days.
Next step was to position the wood. I purchased a tree stump off of eBay, in part because of this pic of Shawn's colon tank.
member-s-frogs-vivariums/topic35018.html
The piece came to big for my small tank, so I had to cut it down to size. Here is a pic before I cut it.
I used a hacksaw to trim it up, and I don't will that pain on anyone, ever again. Do NOT use a hacksaw for this job unless you want an extended workout.

As I trimmed the piece of wood, pieces kept breaking off (not surprisingly). This was because I didn't have a vice, so had to hold onto stump as I cut it. Some good advice, USE A VICE!
Thats all for now :wink: