breeders will feed shrimp regularly, shrimp is extremely cheap in bulk in asian and warmer countries. Also farms will breed millions of roaches for their aros. They then take literally buckets of roaches and steam it to sterilise, then feed to the fish. Crickets are also done but harder than roaches, roaches will breed easily. they dont breed american roaches though, its a different type, not sure but it is flightless roaches.
as for zoos, it will be fish fillets (tilapia i hear is common) shrimp, pellets (commercial pellets made in bulk, usually trout or salmon pellets) used in aqua culture.
in breeding ponds, the aros also eat food naturally occuring, frogs, reptiles, snakes etc. ANything that hits the water really, you may not think thats a lot but just imagine how many animals roam around grass and the rural areas where they breed, that helps too.