I notice in your sketch the baffle leading to the return chamber forces the water over the top instead of below. You should re consider the locations of the baffles so the water will flow below the baffle into the return chamber so air bubbles will not be created and forced back into the display. The bubbles will make the water appear almost cloudy in the DT.
To reduce the cost, I used ceramic tile to build the baffles. It was a lot cheaper than either glass or acrylic (about $1 per baffle). Also, depending on the size of your return pump, you may need a larger return chamber than what the sketch seems to show. I use an external bucket for the ATO water instead of using a chamber in the sump. Although, my sump is a 29 gallon tank rather than a 40 tank.
