Culturing Daphnia

Daphnia also known as "Water Fleas" are one of the most favorite foods for fish. Fish will usually go crazy for them. An adult daphnia is about the size of the letter "a" right here on the screen. But of course there will be babies and subadults of all sizes in the culture. So even if your small fish can't eat an adult daphnia they can eat the smaller ones and all the babies.

For many years oldtimer aquarist would go out to small ponds and wade around in the muck to catch their own daphnia. Thankfully nowadays you can quite easily raise your own.
Heres how:

What you need


Getting Started


Maintaining Your Daphnia Culture

Daphnia will do quite well at normal room temperature, around 68 to 78° F (20 - 26°C). If you're using yeast to feed your culture you want to add only enough to keep a slight haziness in the water. Never overfeed the daphnia. So you might need to feed the culture once a day or possibly every 2 days or maybe even longer between feedings. If you feed too little your culture will not produce as much, but if you overfeed you will kill your culture. If using green water you can be more generous.
When your culture gets going well, usually within a week or so, you can start harvesting. I use a "brineshrimp net" which is just a very fine mesh net that you can get at just about any local petshop. Just swish the net thru the culture and then invert the net into your fry tank or other aquarium that you are feeding. Alternately you could invert the net in a cup of water and use an eye dropper or turkey baster to dispense the daphnia to different tanks.
The dapnia culture will need a partial water change every so often just like a regular aquarium. But don't use fresh tap water, daphnia are very sensitive to chemicals that are present in fresh tapwater. I use old aquarium water, not only is it already "seasoned" it has tiny microorganisms that the daphnia will eat. I siphon about 25% of the culture water thru a fine meshed net to catch any strays that would have otherwise been lost. Then just refill with the old aquarium water.


I buy the small jar of Fleishmans yeast and keep it in the fridge. Take only a small pinch of the yeast and put it in a small vial (I use an old pill bottle) add a little aquarium water and shake it up until well mixed. Then I use an eye dropper to add only enough of this mixture to very slightly cloud the daphnia culture water.

Green Water

Green Water is nothing more than algae water. Just sit a bucket or old aquarium full of water out in the sun and it should go green within a few days. If needed you can add a few drops of plant fertilizer.
You can feed the green water more generously to the daphnia than the yeast mixture as it really doesn't pollute the water. Green Water alone can also make a very good first food for those extremely tiny fry.

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