Pretty neat! I actually envisioned doing the same thing while I was constructing our movie room (in basement) - however, couldn't swing the finances on both the major construction and fish tank endeavor simultaneously.
I did do the top/bottom fish tank thing (190g top, 125g bottom). The trick is that the bottom tank needs to be at least 6" to 8" off the ground and the pump(s) have to be located at ground level. If the tanks are drilled at the bottom, just attach a 90 degree bend on them and feed the pipe/tube straight out to the pump(s). Of course, you probably can do this several other ways (ain't plumbing fun).
Anyway, congratulations on doing a wonderful job. It looks great!