I have tossed the topsoil in without mineralizing it. It can work, no guarantees that it will work for you. It depends on the plants, the lights, your CO2 system, and your water source. I have great water, moderate lights, a pressurized CO2 system, and a love of plants that root heavily (i.e. few stems). So do what you will, keep a journal, and let us know how it goes.
Aquascape? I'm a crypt farmer.
It's a fine line between fishing and standing on the shore looking like an idiot.
That IS an aquascape, it's titled "The Vacant Lot".