There are two doors on top of the tank. It has an automatic water changer. It works off timers, pumps and solinod valves, see link in sig for the details.
I found a short video I took of the tank just after setting it up. The water was still cloudy, still cycling, no fish, but it shows one of my favorite things about the tank - the plants flowing int he water.
This was taken at the same time, shows a little more of the tank. The cabinet was completed yet so the top and sides were open. Click the link to see in higher quaility http://www.youtube.com/watch?v=W0Gf0z4_qNQ