I built myself an acrylic box so that I could get some top down shots. It is ugly as sin, and I would never go selling it, but it is water-tight, and cost me 7 bucks, so I guess I can't complain. Its dirt cheap plexi that I cut with a circle saw (yeah that didn't work as well as I'd hoped) and then learned to score with a knife and break for a cleaner line, super glued to hold it in place, and then siliconed to make it water-tight. Here's some shots of the box and my tank...