not dumb at all..I asked the same question to the people at the Rainforrest Cafe where they have those large round tanks. They use a special rounded brush.
Most of the living color tanks have a resin insert that is treated with a film that "prevents algae" from growing on the insert itself. Up close they look very fake and they still get covered in algae no matter how much you clean. The larger systems have great filtration and features, they just look like fake crap in a tank. Would use these for reef, just FO.