Beautiful! :D
Oh thats absolutely stunning!
It would be odd to put a waterfall in a tank, especially one that size, at 4x4 tiles its huge.
It could be a surface item, but that would look very strange because it would seem too heavy to float on the water.
However an Oxygenator could be made with the top two tiers and have bubbles going up which would be placed inside a tank and look very cool with the Atleantean Tank Wall.
:D