Adult goldfish care assumes a fish large enough to find broadcast food, strong enough to swim against a filter return, and hardy enough to shrug off a water change that runs a little late. A baby goldfish in its first weeks is none of those things. It needs food measured for a mouth that takes crumbs rather than pellets, fed little and often; water kept cleaner than an adult tank needs, because a crowd of fry fouls a small volume fast; filtration that cleans without pulling; and protection from adult mouths, including its own parents. Get those four things right and the first weeks become a steady routine of feeding, siphoning and watching growth.
Feeding Little Mouths, Little and Often
Newly feeding fry start on very fine foods, such as infusoria-rich green water or finely powdered fry food, and graduate over the following weeks to larger items like newly hatched brine shrimp and crumbled flake or pellet as mouths grow. The step up in food size should follow the fry, not the calendar: offer the larger item to a few fry first and watch whether they take it cleanly before the whole batch changes over. Feed several small meals across the day rather than one or two large ones. After each feed, look along the row of bellies: rounded, slightly full bellies across the batch mean the meal reached everyone, while a mix of full and empty bellies means food is landing where only part of the batch feeds, so scatter the next meal more widely across the surface or along the tank. Remove uneaten food once the fry have fed, with a length of airline tubing used as a fine siphon, because a turkey baster or gravel cleaner is far too coarse and hungry around fish this size.
Water, Filtration and Temperature Kept Gentle
Change small amounts of water frequently rather than large amounts occasionally, matching the replacement water to the tank temperature before it goes in, and siphon from the bottom where waste and dead food gather. Fry live close to that bottom layer in their early days, so the centimetre carrying the waste load is the one they breathe. Run filtration that cannot trap or exhaust them: a mature sponge filter driven gently is the usual choice in a fry tank, because it gives biological filtration, a surface fry graze microbes from, and no intake that can pin a weak swimmer. If a powered filter must be used, cover its intake with fine sponge and baffle the outflow so fry are not swimming against a current all day. Keep temperature steady and make any change gradual across a day. Keep handling to a minimum, and move fry in a scooped container rather than a net while they are small.
Separation, Space and Sorting by Growth
Raise fry away from adult goldfish. Adults eat eggs and will eat fry that fit in their mouths, and a mixed tank also puts fry in competition they cannot win for food broadcast at adult scale. Plan space for growth from the start: goldfish grow quickly in their first weeks when fed well, and a rearing tank that suits two hundred fry on day three is crowded within the month, so have the next volume ready rather than improvising when water quality starts to slide. Sort by size as the gap widens. In any batch, some fry race ahead, and the runts get less food, grow more slowly and fall further behind each week; grading larger and smaller fry into separate groups, each fed at its own scale, rescues the smaller group without holding the larger one back. Keep notes by week: food stage, water change pattern, numbers remaining and visible size range. Those few lines per week are the record that tells you what to repeat with the next spawning. Care Teams through KinsLe divides those feeds, changes and weekly notes between keepers, so no single person has to be beside the fry tank at every hour the fry demand.