What I would do is run your lines through the bulkheads, and inside the tank get another acrylic cylinder a little taller than the bottom of tank to just above the waterline to sleeve over
the holes/bulkheads and weld it to the bottom so that this "chamber" will be dry inside... Hang your inlet/outlet on this like it was the rim of your tank, but inside instead of outside... Then you could silicone rocks to this, to hide your inner tube and make a cool "center backdrop". The downside is that you would'nt see through the whole tank at once, but this IMO
would be the shizzle. The filter outlet on the bottom won't help the surface exhcange of oxygen much, and the suction/ejection being so close to each other may make a weird current at the bottom that may make your livestock nuts or be inneffective... Acrylic tube wont be cheap tho, either. Maybe you can do it with 4" PVC
? Really this is just an "overflow" but you already have the cannister.