Join Date: Jul 2008
Location: Northern Florida
Most folks would say you're safe up to a ~100 gallon tank. The only thing that would concern me is an iron stand (seeing as the legs are pretty small, leading to a high punching load on each leg). Most wood stands distribute the load pretty well, so I wouldn't mess with the plywood. It would likely give you more issues than what it's worth. Good idea keeping it along a wall though.
I got lucky moving into my new apartment. All of the floors are solid concrete, so I have nothing to worry about. Just make sure you never have a leak, or your neighbors below you might become enemies. I had to ask before signing the lease that large aquariums are allowed, some places discourage it (or make you pay a larger security deposit).