The Yolk Sac Window
Most egg-layer fry carry a yolk sac for 2 to 4 days after hatching. They do not need food during this phase, but clean water is critical — ammonia spikes during the yolk sac phase kill more fry than starvation.
Once the yolk is absorbed, fry become free-swimming and must eat within 6 to 12 hours or they begin to deteriorate.
Tier 1: Infusoria (Tiniest Mouths)
Infusoria cultures grow from a jar of aquarium water, a piece of hay or banana peel, and 48 hours of warmth. The resulting single-celled organisms are small enough for even gourami and rainbowfish fry.
Dose 5ml per fry tank 3 times daily for the first 3 days.
Tier 2: Baby Brine Shrimp
Baby brine shrimp (BBS) is the gold standard for fry over 3mm. Hatch eggs in a 2L bottle with airstone, 25g salt per liter, and bright light for 18 to 24 hours.
BBS triggers hunting instinct and delivers protein plus essential fatty acids. Drain through a 150 micron sieve and rinse before feeding to avoid salt accumulation.
Tier 3: Microworms and Vinegar Eels
Microworms fill the gap between infusoria and BBS. Culture in oat paste — harvest daily.
Vinegar eels are small enough for bettas and killifish fry. Cultures run 6+ months before exhausting.
Feeding Schedule
Feed 4 to 6 small meals daily for the first 2 weeks. Fry cannot store energy — frequency beats volume.
Remove uneaten food with a turkey baster every feeding. Rotting food causes most first-week losses.