I am planning on building some plywood and glass tanks myself. They really are not any cheaper than buying though. Unless you do make a bigger sized tank. For example, it is quite a bit cheaper to build a 500 gallon tank than to buy one at 2,000 dollars or more.
And actually, I can build two 20 longs for about what it would cost to buy them, maybe not one, but two - yes. Plus have a little materials left over for some more projects.
I would say if you are like me and plan on having quite a few tanks eventually, and you are into DIY, start off with a smaller one first. At least that is what I am planning to do. And I figure if you mess up, better on a smaller less expensive project. And I am sure I will, and if you do, we will learn things in the process that will help us when we do the bigger ones.
And I am pretty sure ones in the 200+ range would be cheaper too. 3/4 inch exterior grade plywood cost about 22 dollars where I live. I can get SW Duraplate 235 for 32 dollars a gallon, which could probably do a couple of tanks in the size range you are talking about? Not exactly set on that yet though. But a local fish hatchery where I live uses it, so I am guessing it can stand up to the static pressure. (Guessing they would be pretty keen on that) Of course there are quite a few choices I have found in my research on how to finsih off the inside. And G.E. Silicone I, which to the best of my knowledge is an excellent choice is not to terribly expensive at a local home improvement store. I think that is what All Glass Aquarium Silicone is. Just repackaged and the price jacked up. And I checked on the price for the glass locally where I live for a 140 gallon, and it was only gonna cost about 45 dollars. I am guessing one for a 500 gallon would not be to terribly expensive? would be the same demsions, probably thicker though? The only real difference between the two in that size I want to make is depth. It would have been almost eight feet long and almost two feet high piece of glass. Of course I have heard glass prices can vary dramatically depending on where you live.
Now that I think about it though, height has more to do with thickness than how many gallons it is.
