Seed mix, refreshed the finch way
Zebra finches live on small seeds, and a finch mix built on millets, canary seed, and other fine grains is the correct daily staple for these tiny Australian birds. The daily skill is in the refreshing: finches hull each seed at the dish and drop the shells back, so by evening the pot can look full while holding mostly husks. Blow the shells off or replace the top layer every morning, and check that actual seed, not debris, is what your birds are finding. In a group aviary, use more than one feeding point so lower-ranking finches eat without being chased off.
Greens and extras at finch scale
Fresh food must arrive in finch-sized form. A small piece of leafy green clipped to the bars, finely grated carrot, tiny broccoli florets, or a little cooked sweetcorn are all taken well once the flock learns them, and birds often start by bathing against a wet leaf before tasting it. Portions stay small because uneaten fresh food wilts fast among a busy flock, and what is left should come out the same day. Fruit is a minor extra, a sliver of apple now and then, rather than a daily feature of this species' bowl.
Egg food when it really matters
The one addition that transforms a zebra finch diet at the right moment is egg food, a soft protein-rich preparation offered in a separate small dish. Outside breeding, a little once or twice a week is plenty for adult pet finches. When pairs are laying, incubating, and especially feeding chicks, egg food should be available daily, because nestlings grow at a speed that seed alone struggles to support, and parents ferry soft food to the nest constantly. Watch breeding birds' condition and remove uneaten egg food daily, since it spoils faster than anything else in the cage.
Calcium, millet, and water
Fix a cuttlebone where every bird can reach it and replace it as it is worn down; hens producing eggs draw heavily on calcium, and growing youngsters need it for bone. Millet spray is the finch equivalent of cake: hang a short piece occasionally for a flock treat or to tempt a bird that has just moved cages, rather than leaving sprays permanently, which unbalances an otherwise good staple. Drinking water goes in shallow dishes or drinkers cleaned and refilled daily, and most zebra finches will also bathe daily if given a shallow bath, which they approach with noisy enthusiasm.
Reading a flock at feeding time
Zebra finches are active, beeping, first-to-breakfast birds, so the individual that sits apart, fluffed and silent while the flock feeds, stands out if you watch for a full minute each morning. Weight is hard to judge on a bird this small, so behaviour at the seed dish and bath is your early-warning system, and a finch that stops eating needs an avian veterinarian quickly, because reserves are measured in hours, not days, at this size. For the daily rhythm, KinsLe's Care Teams assigns your finches' seed refresh, egg food, and water change to named keepers, each job timestamped when done.