When I moved to a new house, the steel stand of my turtle aquarium did not fit the car, so I built a new stand out of two-by-fours.
Step 1: Materials
I used eight two-by-fours, two thin sheets of MDF and some Styrofoam. I also used 88 Phillips screws (80 mm) and some hot glue (for the Styrofoam top). You could add wood glue to all wood-to-wood joints for added strength. I did not bother because it makes a mess and because I want to be able to take the stand apart again.
Step 2: Tools
I used a miter saw because it is fast and it cuts straight, but you could use just about any saw: a handsaw, a jigsaw, a circular saw, a table saw, a band saw, ...
I also used a cordless drill and a hot glue gun.
Step 3: Cut Lengths
I made a cutting list an cut the pieces of wood to length.
Always remember to wear ear protection and safety goggles when using the miter saw.
Step 4: Make the Top and Bottom Frame
Join four short pieces and two long pieces with screws. Pre-drill and countersink the holes for the long screws.
Step 5: Add Corner Pieces
Screw the long pieces in the corners.
Step 6: Hammer in Extra Support Pieces in Corners
Add two shorter pieces to every corner. These pieces should be a tight fit and should be hammered in place. Add some screws to permanently secure these supports.
The aquarium will now be supported by a total of 12 upright pieces, which is more than enough for my 200 litter tank. You could add extra supports in the middle for larger tanks.
Step 7: Optional: Glue Styrofoam to To Top
Styrofoam helps evenly distributing the weight of the tank, especially if the top of the frame is not perfectly flat or if the tank is made of acrylic.
Step 8: Add Shelves
I added two thin sheets of MDF. The bottom is attached using some short screws and the top one using hot glue.
Step 9: Add Aquarium, Move Turtle, Etc.