A tank built in your wall cleans like a normal aquarium. The only difference is that you will have a little less elbow room. With an in-wall tank you might have to lift open or remove a trim-door to gain access to the top of the tank. The aquarium does not move or get taken out of the wall; you simply put in your hoses and give the tank a scrub if needed.
Once a month or more you will have to remove 25 – 50% of the water and replace it with tap water. You will siphon the water out through a hose into a bucket or drain. This hose has a larger end that is used to vacuum up the waste but not the gravel. To fill, a hose hooked up to a water supply is used. You will have to add water conditioner and salt.
For advanced set-ups you can plumb the water intake and drain tubes to the aquarium for ease of maintenance. See this blog post for details