There is actually no such thing as self-cleaning.
All fish tanks (in the wall or not) require regular maintenance due to the fact fish product the toxic ammonia as waste, and in a well established tank the ammonia is converted to relatively harmless nitrate by the good bacteria developed in the filter media over time. However, nitrate at extremely high level will weaken the fish's immune system and thus making them more easily catching diseases and parasites. Nitrate as well as some other organic waste is not going anywhere even in a heavily planted aquarium. It is why weekly partial water change is highly recommended for optimized water quality for your pet fish.
In my personal opinion, an aquarium mounted in a wall might look cool and save space, but it is not easier to maintain than any other fish tanks.
