Thank you everyone for the kind words. I feel it looks good for my first shot. It took a bit to find out exactly how the sand would fall. My design has 3 major rocks the base that also acts as part of the catch. Then the main rock the sand cascades down. Then a top rock to push the sand down and hide the 90. I played around with the angle of the rock for about a week. (by the way nothing else was in the tank) I would set the rocks up observe the way the sand was falling. I had to make adjustments too the angle to make it more steep, or less. I also had to adjust to make sure the sand fell down the path I wanted. The base would also get moved with every adjustment to make sure the main rock would sit correctly against the glass, also to make sure sand was returning to the PVC. This was the longest part of the process. I sadly scratched my glass during this phase so be careful. As far as adding sand, I had to make small adjustments once the tank was fully set up. I added small stones in key area where I noticed sand was spilling off. This worked very well. I also had to add small amounts of sand the first few days as it began to settle and fill cracks. It's now been a week since I last added any. Here are some pictures of the catch basin. Sorry that one is at an angle it wad the best way to show it. By the way PVC may work as well but you may have more trouble with the sand drifting away from your catch.