i dont think ive got about 29 fish in my 29 gallon tank all ranging from moderate to small, and im horridly horridly overstocked, but, ive never kept the fish your interested in so hopefully some other members will come along and assist you, i do know however, if your were to keep just five more of each you should be ok, the popular suggestion for bottom feeders seems to be khuli loaches, ive never seen em at my lfs but apparently alot of memebers like em, check em out, i think those travel in packs too, not sure, hope i helped!
Yup, as Buenos Aires tetras can get pretty big, I'd go with peacemaker. Them maybe get 5 or so kuhli loaches. But make sure that you have some hiding spots (like caves or sand) for the loaches to hide in. They do like to burrow.