Size rules the first weeks, not the calendar
A fry can only eat what fits in its mouth, and mouths in the same batch grow at noticeably different speeds, so the honest guide is the fish in front of you rather than a date. In the earliest stage the foods are effectively liquid or alive and tiny: infusoria, liquid or powdered fry food, then newly hatched brine shrimp and microworms once the fry are big enough to take them. Feed little and often, several small meals through the day, because tiny stomachs empty fast and growth at this stage is rapid when food is constant. Watch the smallest fry as your benchmark — the runts set the pace for when the whole batch is ready to move on, and separating the biggest few into another grow-out space stops them monopolising every feed.
Bring crushed flake in alongside, not instead
For many common species the second or third week is when flake can join the menu. Grind it to dust between finger and thumb at first — finer than you think necessary — and sprinkle a small pinch in with a live feed, so the fry strike at the mixture and learn the flake is food along with everything else. Over the following days, raise the flake share and ease the live foods down rather than swapping in a single step; fry that go off their food during an abrupt change lose growth you cannot easily win back. Some flake will always be ignored and sink, so keep portions genuinely small and siphon the bottom afterwards, because a fry tank's water quality is the first thing sloppy transitions ruin.
Coarsen the grind as the mouths grow
Each week, grind a little less. Dust becomes crumbs, crumbs become small fragments, and before long the young fish are taking small whole flakes and micro pellets without help. This is also the stage to widen the menu: finely grated frozen foods, crushed pellet, and slightly larger live foods all teach the fry to accept variety, which pays off for the whole of their lives. Judge each step-up by the post-feed bellies — rounded but not swollen — and by growth staying even across the batch. If the smallest fry start falling behind at a coarser grind, hold that tank at the finer size a few days longer; there is no prize for moving every tank on together.
When fry are effectively eating adult food
The transition is complete when the young fish attack small whole flakes and micro pellets with the same confidence they showed for live food, and growth stays steady on three or four feeds a day. Keep feeding more often than you would adults — juveniles are still building body mass — and keep grading by size if the spread widens, since a mixed batch on one food size always short-changes somebody. Writing the current grind size and food mix for each grow-out tank into KinsLe Care Teams keeps the week's stage in front of anyone who feeds while you are out.