For a rectangular glass tank- you can silicone the black piece of plastic as a back wall, may be add dividers, if you prefer it this way - for filtration media, heater, return pimp, and refugium - like Nano-cube has.
This wall could be drilled to accommodate bulkheads - the hole between the display part of the tank and the back chamber, allowing attaching nozzles and the hoses to the pump.
Example .
Or make it over the wall, like
here. The idea of closed loop can be seen also
here, the grey "T" and 90 degree connectors from the plumbing department of hardware store, and the clear vinyl tubing to fit them (same source), can be gently heated to fit.
And the intake hole with teeth for surface skimming, like
here, in the top corner, left, for example. The main water return will be at the other, right top corner, so water will flow through all the length of the back chamber. The return pump will be at the bottom.
More links with the same idea, but for different scale:
brandon429 tank,
corner or back wall divider,
trapezoid in the middle of the tank, that doesn't require closed loop - two pumps are oriented in opposite directions; this is like
brandon's .
Anyway, you can always add Mini-Jet 606 for additional flow in any part of the tank, will be visible, but this is flexible solution - if don't need - just remove it.