While thinking about how to move a couple of smaller tanks full of fish into a new house, it occurred to me to get a new large tank, set that up first, move all of the fish into the new tank, then move the empty old tanks. After scanning Craig's list and making a couple of phone calls, the next thing I knew I had 200lbs of empty glass tank sitting on my living room floor and a major design/build project taunting me. I ended up moving the small tanks with a few inches of water and fish in the bottom, months before finally getting the new tank set up. It turned out to be much more difficult than I anticipated to come up with a functional tank stand I thought I could live with for the next decade.
Design Constraints
The aquarium is going to be located in a large room with a modern design aesthetic: the floors are polished concrete, while the walls and ceiling are a combination of glass, brushed aluminum, wood and stucco with some prominent exposed steel structural elements.
The tank is 125 gallons: with water and rocks the dead load to be supported is approximately 1500 lbs. Also, the house is located about 1 mile from the San Andreas fault, so the stand needs to be quite strong with respect to lateral shear forces.
Design Process
I spent close to two months iterating on design. I initially considered conventional wood frame/plywood sheathing designs, but didn't like the look. I wanted to get away from the 70's rec-room vibe it conjures up for me. I also wanted to avoid a hulking appearance, so I played around with leaving parts of the stand unenclosed. I figured metal framing would allow the most design possibilities.
As usual, all of the difficulty came in trying to strike the right balance minimizing cost (roughly amount and kind of material used) while maximizing design capabilities (where more and more expensive material helps).
Update: I originally intended to say something about the technical design process, but that was almost 3 years ago. The short story is that it's possible to estimate the deflection of a beam under load by standard equations and engineering specs for your material, but very difficult, so far as I could learn from the web, to estimate how much stress a joint can bear without failing. Accordingly I probably over-sized the beams in use, and put a lot of effort into designing sheer panels to prevent the frame from collapsing laterally.
Here's the final sketch I emailed to 80/20, who converted it to a CAD drawing.
Here's the kit from 80/20 laid out and ready to assemble. I was impressed by the accuracy of the cuts and other machining. It was better than the tolerances promised. The frame went together very square without any trouble.
Starting to attach the cross pieces to the front/bottom beam.
Bottom together, but still only loosely.
First vertical columns going up.
Perimeter beams & columns set up, cross pieces going in loosely.
Cutting the plywood shear panels. I used 11/16 plywood, and glued two together for a final thickness of just under 1.5", which gave a slight inset from the aluminum framing on the faces. I cut the panels 1/32" oversize, then tightened the frame around them on installation. Since the 80/20 machining accuracy was very high, this worked out quite well.
The outer panel faces were stained before cutting and gluing. After gluing I did a touch-up staining, and then several coats of urethane for water resistance.
Two pieces of shear panel clamped after gluing.
The top is a single thickness of 11/16th plywood. There's an invisible back shear panel that leaves space for plumbing/electrical at the sides. Here I'm fitting both panels prior to finishing and attachment.
The finished shear panels that are externally visible are attached by friction (tightening the frame around them), and also by internal bolting to the frame. My design guess is that this increases shear strength of the frame considerably. However, I don't plan on any destructive testing to confirm it.
Front view of the three visible shear panels.
Back shear panel installed.
Fitting the equipment cabinet door. I left 1/16th inch clearance around the edges, and wedged it into position with cardboard while marking where to drill holes to fasten the hinges.
Internal view of where the door hinges will attach. Structurally, this is an inset frameless cabinet door. The usual hinge would be a European style with a mounting cup drilled out of the door face. I didn't want to buy extra gear just to drill a couple of holes (and don't have a drill press either), so I looked around a lot and finally found some nice self-closing hinges of with the right properties, online at San Diego Hardware.
Hinges installed.
