Hi, a great read from beginning to end! I love the simple design. You have really got me thinking. Running the inlet pipe back into the tank, just below the surface would probably cut down a bit on the water splash noise also? I started out with tropical fish about 6 months ago, got into Discus about 4 months ago (been on a steep learning curve!) and have gone from a 4 foot, to a 6 foot and now setting up a 8.5ft 1100lt display in the lounge. I have just bought a Eheim 2080 and was thinking of buying another one in the near future to have a decent amount of filtration once the tank starts to fill with stock. At $800 with media, they are not cheap. This is a great area to save some money and end up with a very useful and satisfying filter addition. Just need to come up with a way to disguise something like this that keeps the wife happy...hmmm, maybe try and place it behind the tank and plumb through the back of the hood?
I find myself looking up large acrylic tank builders in China, out of interest, on the net in my breaks at work. Where will the madness end....... : )

Cheers