The tank has one, but with this method the fish waste is meant to be absorbed into the soil, so an undergravel filter isn't needed. Diana Walstad recommends using no CO2 set up with her method, as that causes plants to take nutrients out of the soil faster than they can be replenished. An air bubbler can be used, but isn't needed, as if there are enough plants the fish will get enough oxygen. I'll get some pics up later today, as I'm still setting everything up. There are some wonderful pictures I've seen online of tanks set up like this though.
Keith
I had a salt water reef tank for many years. I keep telling my wife I want one again. We have collected shells and coral from beaches all over in anticipation of another reef tank, but have not got around to it yet. Someday... I have seen some really cool freshwater discuss tanks with lots of live plants.
Dave