What fish do you have currently aside from tetras? What species are these tetras? Otos or ancistrus can consume algae while cories can eat foods at the bottom but this should not give you the impression that they do not eat food supplements. Like other fish, they still need to be provided the proper foods you can give them. If I were you, I'd rely on a magnet algae scrubber and a gravel vacuum.
Do not drop too many food at once. Feed gradually to minimize the chances of food falling to the bottom which can result in fouling of water.