This is not that risky of an endeavor with the proper bracing installed in the basement. If the op has no background in construction then I would for sure recommend contracting someone who does to be sure the floor is properly supported. Another comment that may be off base is to sat that a diy plywood tank is going to look like crap in his living space. I'll be making a plywood tank in the next few months that will be the centerpiece of my office and it will look every bit as nice as an acrylic setup that was recommended for a fraction of the cost.
