Thanks guys. I ended up going with a bare bottom tank. When I had the alligator inside, we used sand, and the more I thought about it, the more I realized how often I had to clean that tank even with filtration. Right now, I've got the guy in a 120, bare bottom, with a nice HUGE floating piece of drift wood, some water lettuce and water hyacinth, and a solid internal filter. Water is staying crystal clear and he's got space to hide if he wants to or be out in the open.