Quick answer: daphnia are tiny freshwater crustaceans, often called water fleas, that live in ponds and lakes. Freeze-dried, they make a light, protein-rich food with plenty of fibre from their shells. Aquarium fish, young turtles and terrapins, freshwater shrimp and snails all eat them, and so do isopods, millipedes and springtails. Feed a pinch at a time and keep the bag sealed and dry.
What daphnia are
Daphnia are small crustaceans, a few millimetres long at most, that swim through still fresh water with jerky strokes of their antennae, which is where the water flea name comes from. They filter algae and bacteria out of the water and are in turn one of the main foods of small fish and other pond animals, which is why they have been a fish keeper's standby for as long as there have been aquariums.
Our dried daphnia is the whole animal, freeze-dried, with nothing added. It runs to around 50% protein, and the shell adds chitin, which is where the fibre comes from.
Live, frozen or freeze-dried
Live daphnia are the first choice for fry and for coaxing fussy fish to eat, but they need culturing or a regular supply, and anything live from a pond can bring unwanted passengers with it. Frozen daphnia keep well but need a freezer and thawing. Freeze-dried daphnia sit on a shelf for months, carry less risk of bringing parasites or disease in with the meal than live food, though no dried food is sterile, and are ready to use straight from the bag. The trade-off is that they float at first and weigh almost nothing, so they are an extra rather than a filling meal.
Which animals eat it
Aquarium fish
Most community fish, goldfish and bettas take daphnia readily, though goldfish should have it only in small amounts, as our guide to what goldfish eat explains. For a betta, our guide to what betta fish eat shows where it fits. Many fish keepers use it as an extra a couple of times a week alongside a staple flake. Small fish and fry manage it more easily crumbled between the fingers.
Turtles and terrapins
Daphnia suit hatchlings and young turtles best: small enough to swallow whole and light enough to float where they hunt. Larger turtles will eat it too, but it is a light snack for them rather than a meal.
Freshwater shrimp and snails
Shrimp and snails pick over what reaches the bottom, but freeze-dried daphnia floats at first, and soaking does not reliably sink it: of the two keepers' accounts we found, in one it just floated, and in the other only about a fifth had sunk after several hours. For a shrimp or snail tank, a sinking food such as an algae wafer is the surer way to get food to the bottom. For snails, our guide to what aquarium snails eat covers wafers, vegetables and the hard water their shells need.
Isopods, millipedes and springtails
On the invert side, daphnia is a light protein extra. Put a small pinch on a piece of bark or a lid so it stays off the damp substrate, twice a week at most, and clear what is left within a day so it does not draw mould or mites.
How to feed it
For fish, offer a pinch they clear in two or three minutes and net out anything left, because uneaten food breaks down and fouls the water. Freeze-dried daphnia floats at first, which suits fish that feed at the surface; for fish that feed lower in the tank, use a sinking food instead. For turtles, drop it into the water a few pinches at a time. For inverts, keep the portions small and the feeding spot dry.
Storage
Freeze-dried food takes up moisture from the air, and damp daphnia clumps and spoils. Keep the bag sealed in a cool, dark cupboard, and take a pinch with dry fingers. Kept that way, a 100g bag lasts a long time, because daphnia weighs almost nothing and a pinch is a serving.
Daphnia alongside other foods
Daphnia works best as part of a mix. For tropical fish it sits well beside a general flake such as our tropical fish flakes; plant-eating fish such as goldfish also take softened freeze-dried peas; and turtles get more from whole dried shrimp and fish once they outgrow daphnia. For isopods, our guide to what isopods eat shows where a protein extra like this fits. Everything we stock for fish, turtles and reptiles is on foods for reptiles, turtles and fish.
Frequently asked questions
What is dried daphnia?
Whole daphnia, the small freshwater crustaceans also called water fleas, freeze-dried. It is a light, protein-rich food with plenty of fibre from the shell.
Is dried daphnia good for fish?
Yes, as an extra. Most aquarium fish eat it readily, and many keepers use it a couple of times a week alongside a staple flake.
Can turtles eat dried daphnia?
Yes. It suits hatchlings and young turtles best, as a small floating treat. Larger turtles eat it too, but it is a snack for them rather than a meal.
Do you need to soak dried daphnia?
Not for surface feeders, which take it dry. Soaking softens it but does not reliably sink it, so for bottom-feeding fish, shrimp or snails a sinking food such as an algae wafer is the surer choice.
How long does dried daphnia last?
Months, if the bag is kept sealed, cool and dry. Moisture is what spoils it, so use dry fingers and close the bag straight after.
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