A corydoras grow-out tank succeeds on gentleness at floor level. Fry spend their days on the bottom, grazing surfaces and sifting for food, so filtration must move water without pulling at tiny bodies, the floor must stay clean without harsh siphoning, and every meal must actually reach the bottom before stronger tankmates or currents take it.
Choose the Tank, Floor, and Water First
A modest tank of about 20 to 40 litres (roughly 5 to 10 gallons) suits a typical home batch of fry and keeps food concentrated near them. Fill it with mature water from the breeding tank, or with dechlorinated water matched closely for temperature, so fry move into familiar conditions. Leave the floor bare for the first weeks, which makes waste visible and siphoning precise, or spread fine sand in a layer no deeper than about a centimetre (under half an inch) once fry are feeding confidently. Coarse gravel is a poor choice, since food falls between stones and rots out of reach. Keep the water level moderate and the lid fitted, and place the tank away from doors and speakers that thump vibration through the stand.
Run Gentle Filtration That Cannot Trap Fry
Use a sponge filter powered by an air pump, sized for the tank and seeded in the breeding tank or an established aquarium for a couple of weeks beforehand so it arrives carrying working bacteria. Air bubbles rising through the lift tube draw water slowly through the foam, cleaning it without any exposed intake that could pin or swallow a fry. Set the air flow low enough that fry rest on the floor beside the sponge without being pushed sideways. The sponge surface itself becomes grazing ground, holding biofilm and trapped micro-food that fry pick at between meals. Rinse the sponge only in removed tank water, a gentle squeeze at a time, and never under a tap.
Arrange Low Cover and a Feeding Routine for Bottom Life
Give fry shelter that sits on the floor: a small stack of smooth pebbles, one or two pieces of prepared leaf litter, and a loose clump of moss. Keep the centre of the tank open so you can watch feeding and count fry roughly each day. Feed foods that sink and stay small: microworms and newly hatched baby brine shrimp for young fry, then finely ground sinking pellets and crumbled bottom-feeder wafers as they grow, in small meals three or four times a day. Corydoras fry feed by grazing and sifting, so scatter food across the floor rather than dropping one pile. Remove any film of uneaten food during the daily siphon before it clouds the water.
Keep the Floor Clean With Little-and-Often Changes
Siphon the floor gently with airline tubing every day, drawing off waste and a small volume of water, then top up slowly with matched water poured over a saucer or your hand so the current does not scatter fry. Small changes of about a tenth to a fifth of the volume, done often, hold conditions steadier than a large weekly change. Test ammonia and nitrite during the first weeks, since a young sponge and frequent feeding can drift out of balance quietly. Move fry to the main tank only when they are clearly too large for any adult mouth there and are feeding boldly in open water. Recording each feed, sponge rinse, and floor siphon in KinsLe through Care Teams keeps the grow-out routine intact when a busy week hands the fry to someone else.