^^^^^
You can't find a fish that will eat waste. What you can do is heavily plant the tank. Plants will take care of the nitr(a/i)te (I forget whether it's nitrate or nitrite) buildup. But, even then, you will have to do a little cleaning. In my Krib tank, I am planning on cleaning the gravel once a month, so as to let the plants grab all nutrients they can.
But, honestly...that's the only way to get out of tank cleaning....and that comes with it a whole other level of complexity, since you now have to worry about lighting, and algae growth, etc.