A lot of people think dividers are ugly, and they get in the way of a nice scape. Using a taller tank inside of another tank can open up whole new worlds of aquascape possibilities. You would have to silicone the smaller tank inside the larger one, and leave space all around for water flow I think. And come up with a way to circulate the water through both without drilling them, and without making it look ugly. I think those would be your biggest speed bumps.
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