You do not have to feed bac ammonia to keep them alive, as long as you keep water in the tank they’re alive. Humans don’t control bacterial starvation when a cycle is done by withholding feed, a cycle cannot be undone without medication, antibiotics. Offhand I can think of five mechanisms that provide feed to established bacteria in a home. One chief feeding mechanism is that any tank which had fish in it and some form of surface area will catch particulate organic matter / detritus and that’s near permanent bacterial feed on its own. Secondly there are home contaminations such as a gnat...one unfortunate micro bug falls in, he’s ammonia destined. There are several more...non filtration bacteria that 100% contaminate any home system are always getting in, and dying, reducing to feed right in proximity of nitrifiers etc
wet bac in a use natural acquisition means to stay alive they don’t need our expenditures.