After reading up on all the benefits of deep sand beds, I went ahead and added one to the whole bottom. I've only had bare bottoms in the past, but I'm really liking how the tank looks now. I had to move the tank to make way for some renos, so I figured the imposed low tide was an opportune time to make the change. I got a few bags of the old fine grain silica play sand and went to town. I've heard people saying how silica sand or rocks in the tank will lead to diatom and dinoflagellate explosions, but the test patch I put in a couple weeks ago didn't produce anything. The bed depth is between 4 to 8 inches. It definitely makes it easier to reach the bottom of the 30 inch tall tank.