I keep my smaller snakes in racks too but I can't imagine using big tanks for all my guys that need cages: one factor for me is the weight (we have melamine and PVC cages and though the melamine is heavy too it's not as heavy as those big glass tanks for me) and another is aesthetics. I just don't like the looks of the big tanks unless they're for fish and very much prefer the looks of stackable 4', 6', and 8' caging.