The verticals on the shelving units are split in half. You can make 2 stands for stacked tanks out of one unit. I set up the other half for another tank in a different part of the house. The unit is easy to put together. The only tricky part is the lower tank has to be put in place before installing the top shelf. The tank fits within the L-shaped posts and cannot be installed from the front, only the top, if that makes sense.