Make or Buy Centerpiece?

i think the real thing will always look better.

Out of curiosity, what would you make it out of?

I would just go find one. I'm sure you get make one or get one built, but I don't think it would look as good, and would either be hard and time consuming to make, or really expensive to buy.

The wood looks a lot smaller in nature, and looks a lot bigger in the aquarium. I went to a local lake and was easily able to find several pieces of wood to fit my tank. My tank is only 18" from front to back, and it was surprisingly hard to find good wood pieces that would fit. Most good looking pieces were quite a bit bigger. Make sure to have detailed measurements, and bring a good way of cutting the wood (chainsaw, reciprocating saw, etc). A size big enough to be your center piece will probably be pretty heavy, like 100lbs.

My tank is 84"x18"x18", so quite a bit smaller than your tank, but you get the idea. Left picture is when I laid out and cut the wood to fit to be the centerpieces. I also made a concrete/foam background that I designed around the wood. Finished product on the right.