I must admit that the main reason why I personally am such a fan of plywood is simply the fact that all my experience is with that type of tank construction. Even when I first started building plywood tanks (30-ish years ago), I seem to recall that the minimum size at which they became cheaper on a per-gallon basis than glass was somewhere up around 300+ gallons.
I built a lot of all-glass tanks back in the day, for myself and also while working for a local small business that made them. Back then we used much thicker glass than is typically seen today, making the tanks more costly (for that time period) than they are today and much heavier...but it also made them stronger, more resistant to damage and easier to build.
Virtually all my builds have been either 120 gallons (4 x 2 x 2 feet, made from a single 4 x 8 sheet of plywood) or 360 gallons (8 x 3 x 2 feet, made from three sheets of ply). The tanks themselves contain no 2x4's, so I'm not sure why you have any 2x4's listed at all...let alone 15 of them?
I had no idea that acrylic is now so relatively inexpensive, and I can certainly see the appeal of using it for a DIY builder, but I am curious about one issue: in what manner does an acrylic tank fail? All-glass tanks can suffer massive seam separations, dumping a huge quantity of water on the floor
right now. I experienced one such incident with a commercially available tank...it's actually what led me to plywood construction...and I've helped several friend clean up the aftermath of similar catastrophes. Plywood, if it leaks at all, tends to be a slow, insidious process which is certainly not fun to witness, but it doesn't involve a huge destructive tsunami in your living room. How about acrylics? Do they typically have seams let loose, or is a failure typically a slow dribble? That's an important question to anyone who has had a, shall we say...huge dribble...
L
LukeOscar
, that acrylic build you have posted in another thread is awesome; it's the kind of build that makes me think I should try that technique. I'll probably never do it; I've gotten older, moved into a much smaller house, and my involvement with the hobby no longer revolves around more-more-more and bigger-bigger-bigger. If I build anymore tanks now I'm not really interested in experimenting; I'll just do what I know works for me.
You touched on one particular aspect which few seem to consider: air quality as affected by the construction materials. Most of my tanks are built standing right where they will live their lives...which now means in the basement of my home. Weight is, for me, more or less a non-issue. Large all-glass tanks are no longer on my radar screen, but I still build the odd small one for specialized purposes or for friends, and the acetic acid fumes are fairly inoffensive and easily vented. A big plywood tank can be built with the mild odour of wood glue and some sillicone; the only fumes I really worry about are from the interior sealant. Back in the day those were high-VOC coatings and precautions were strict. Today, coatings like Pond Shield and the Intraseal epoxy I have been using produce greatly reduced levels of "dangerous bad smellies"; I also recently tried my first pond-liner plywood build, using Geocel 4500 as an adhesive/sealant, and was thrilled by the lack of fumes.
What's the deal with acrylic solvents? I am sort of assuming that they are the worst of the worst when it comes to dangerous fumes; yes, no?