Step 1: Materials and Tools
Cutting a straight line along edges that will be watertight is really important. Cut and file edges smooth and you'll be rewarded with a tank that won't leak. I find it useful to build cardboard models of my tanks and then use them as templates for my acrylic.
Step 2: Bending Acrylic
Because the base is already cut to the exact size and shape for the tank, I will make each bend fit the base. Because the acrylic is flexible, exact precision is not required. Nonetheless, we want to make our bends as square as possible.
Clamp the acrylic so that the bend just overhangs the edge of the bench and heat it with a propane torch set to a medium flame. Keep the torch moving! You want to soften the acrylic but not melt it. If you see bubbles, or if a lick of flame is left behind when you move the torch, then you're getting the material too hot.
Once the bend forms, take the clamps off and set it on the base. You'll have a couple minutes to get the bend at just the right angle. Hold it for 3 or 5 minutes and it will cool and harden in place.
After it cools, mark the spot for the next bend with a Sharpie.
Step 3: More Bending
Step 4: The Last Bend & Joining the Seam
Clamp the tank to the base. The goal is to find an exact mark where the excess needs to be trimmed, both top and bottom. Use painter's tape on both sides of the acrylic to minimize chipping and cut. I tried to cut a bevel edge that would hopefully mate with the bevel I'd previously cut on the other end. It worked pretty well considering the lack of precision involved.
Once the piece is cut, I tape it so that it fits the base. FIrst, a lot of tape on the outside while I applied thickened solvent into the seam. Then, turn it over and apply to the outside of the seam. This worked very well for me, I never had even a single drop leak.
Step 5: Attach the Base & Light Tube
Step 6: Test With Water
The light fixture is a 12" florescent fixture with an aquarium spectrum bulb. I built a little stand fro scrap acrylic to hold it up with reach. It lights the tank wonderfully.