This rack is designed to hold two 29 gallon aquariums. It was built using 2x4 pine studs, wood screws, and steel corner brackets. The total cost was less than $50, and the only tools required are a saw and a drill.
I created a 3D model of this rack using SketchUp before I started building so I could check all of the dimensions. A 29 gallon tank measures 30 1/4" Long x 12 1/2" Wide x 18 3/4" High. Note that 20 gallon "long" tanks have the same footprint, but are 6" shorter in height, therefore this rack design also works for 20 longs. Its important to make sure you will have adequate space between tanks when designing a multi-level aquarium rack. This design allows roughly 7" of space between the lower tank and the top shelf.
I cut the 2x4 studs to size using a Dewalt miter saw. The only lengths needed for this rack are 53", 31", and 11". The sketch above shows how they all fit together. I sanded all of the pieces at this stage so that every surface was smooth.
I assembled the shelves by placing the 11" sections on the inside edges of the 31" sections, and securing with 2.5" wood screws. I always drill pilot holes before driving a screw into a stud.
I stained the shelves and the uprights before connecting them all together. Then I assembled the rack in its designated position in my fish room starting from the floor.
To prevent the weight of the aquariums from putting too much stress on the wood screws, I added steel brackets under all 4 corners of both shelves. This design would probably not support a larger aquarium, but a filled 29 gallon weighs only 330-350 pounds. Each #8 wood screw has a shear strength of about 100 pounds. I used 8 to secure each shelf to the uprights, plus the additional supporting brackets, just to be safe.
**Disclaimer: Do your own math - I'm not responsible for any damage caused by this design failing in your application**
These brackets were less than $2 a piece at a home improvement store. They are secured with 3/4" metal-to-wood lath screws.
Currently this rack holds a 20 gallon long fry tank and a 29 gallon planted tank. Although it was designed to hold two 29's, I already had the 20 and decided it would make a good growout for my Endler fry.
See my other DIY rack design here.