- What are daphnia?
- How do daphnia reproduce?
- Are daphnia nutritious for fish?
- What fish eat daphnia?
- How do I store daphnia?
- How do I feed daphnia to my fish?
What are daphnia?
Daphnia are small (0.5 – 3mm), almost transparent, freshwater crustaceans with two feather like antennae and only a single compound eye. Their bodies are enclosed by a carapace and within the carapace they have leaf-like limbs they move to produce a current of water that circulates oxygen and nutrients to their mouth and gills. I reference circus skills because daphnia are commonly know as water fleas! They aren’t fleas though- they have this common name because of the jerky way that they swim. Daphnia use downward strokes of their large antennae to move around and can be surprisingly quick.

Daphnia earned their common name of ‘water fleas’ because of the jerky way that they swim.
How do daphnia reproduce?
The eggs hatch in the brood chamber within the carapace of the female daphnia and the juveniles are released in approximately two days when the female molts – they go on to reach maturity in around 6 to 10 days.
Are daphnia nutritious for fish?
The nutritional value of daphnia varies depending on the water it was living in and the food that was available to it. Studies have found that dry matter content is around 40% protein with 5% fat and fibre and that it provides all the nutritional requirements of omnivorous fish like carp.
What fish eat daphnia?
Daphnia is not suitable for feeding to marine fish as they die quickly in salt water and may break down causing water deterioration. However, daphnia are a great food for any type of freshwater fish.
How do I store daphnia?
Daphnia should be stored, like brine shrimp, in a cool place or refrigerated in the unopened bag they are sold in. It is advisable to use as soon as possible but daphnia should keep for up to a week if stored properly. Here at Cornwall Aquatics we aim to sell all of our daphnia as soon as it arrives but if we have any left it gets stored in our fridge which we have set to 8 degrees.
How do I feed daphnia to my fish?
Daphnia can be added to any freshwater aquarium complete with the water they are supplied in or you can filter them through a net and add just the animals. Ensure the net size is sufficiently small not to let the daphnia through – you will need a mesh of no larger than 400 microns (0.4mm) for this. As with brine shrimp, a bag of daphnia contains enough animals for one feed for an aquarium larger than 24 inches. This is only a guide though as it depends on the number, type and size of fish so make sure you only add enough so that the fish will eat the bulk of them in 15 minutes.
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