The water change is the aeration. By changing out the water regularly, you're mixing oxygen into the tank water. In addition, you have oxygen from the surrounding air in the room and the O2
produced by the plants. There is more than enough O2
to sustain your fish between water changes. Granted, only 1 in 10,000 tank keepers could commit to such an aggressive water change routine, but it can be done.
Back to my point, the filtration equipment, even multiple, high end, expensive filters can't be depended upon to keep the tank water pure. Only large, frequent water changes can do the job.
Just an opinion from a water change fanatic.