Feeding Fish Fry: First Meals and Feeding Frequency
The first days of a fry's life often decide whether it survives: past a certain point without food, its yolk reserves run out and it can no longer recover, even if fed afterwards. This threshold, known as the "point of no return," was first identified in 1963 by researchers Blaxter and Hempel in herring larvae, in a founding study on how egg size affects larval survival (study on Google Scholar). In aquarium fish, the same principle applies: feed early, feed often, and match prey size to mouth size. All our feeding benchmarks are gathered in our fish food section.
The right moment for the first meal
While a fry still carries its yolk sac, it shouldn't be fed: it draws on its own reserves, and any uneaten food just pollutes the water. Once the sac is absorbed and the fry swims freely and horizontally, usually two to five days after hatching depending on the species, the first meal should follow quickly to avoid approaching that point of no return.
Prey sized for a tiny mouth
A fry's mouth is minuscule: adult flakes, even crushed, are often still too large or sink poorly. Infusoria and liquid fry food suit the very first days for species with tiny fry, and freshly hatched brine shrimp nauplii become the go-to once the mouth widens a little, supplemented with microworms or powdered fry food. For livebearers (guppies, platies, mollies), which are born already formed and mobile, finely crushed flake food is enough from day one.
Feed small and often
A fry has a tiny stomach and a very fast metabolism: three to five small meals a day give far better results than one or two large ones, which mostly end up polluting an already fragile tank. Remove uneaten leftovers after a few minutes and favour frequent small water changes over one big one, so as not to stress fish that are still tiny. Our guide to cycling an aquarium explains why a grow-out tank needs to already be biologically stable before the first fry arrive.
Frequently asked questions
Can you feed fry crushed adult food?
Only once they're big enough to swallow it; in the first few days, the pieces are almost always still too large.
How long do hatched brine shrimp nauplii stay good?
They stay nutritious for about a day in aerated salt water; beyond that, their nutritional value drops sharply and it's better to hatch a fresh batch.
Do fry need a separate tank?
It's strongly recommended: in the main tank, most fry get eaten by the adults before they even get their first meal. Find all our guides on the aquarium hub.
This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.