How to Culture Daphnia

The Daphnia, or 'Water Flea'

Daphnia are small, freshwater crustaceans found in most ponds and lakes. They are a favorite live food of tropical and saltwater aquarium fish. The two most common species, D. pulex and D. magna, are what we will be culturing to feed our fish. I have had some success doing this, and I'll share that with you.

Things You'll Need

• At least two 5-gallon buckets
• Aged, clean water
• A daphnia starter culture

Instructions

1. START A GREEN WATER CULTURE -- Daphnia feed on unicellular algae, or 'green water.' You must have an active culture of algae to feed your daphnia. Place your buckets of water outside in direct sun if it's above 60F. Otherwise, what I do in the winter is keep my buckets indoors under bright lights 24 hours/day. You should get green water in several days or weeks.

2. GET A DAPHNIA STARTER CULTURE -- You can buy Daphnia pulex or Daphnia magna online. I have a link at the bottom to a site. You can also collect your own from a local pond or lake. Daphnia are attracted to light. What I did once was, at a local lake at night, I held a lantern out over the water. Within about 10 minutes, I had 1000s of Daphnia swarming up to the light. Just collect some lake water in a jar, net them, and put them in your jar. Easy!

3. 

   INTRODUCE YOUR DAPHNIA CULTURE -- You should not be able to see through the water - yes, it's that green. Dump the starter culture of daphnia into one of the buckets. Maintain the light source over all the buckets to keep the algae growing.

4. 

   HARVEST AND PROPAGATE YOUR DAPHNIA -- As the daphnia grow and multiply, they will eventually consume all of the algae in the water and it will become clear. This is why you have more than one bucket. Harvest the daphnia from the first bucket and feed these to your fish, while you take another starter culture from this and add it to another bucket full of green water. You should have at least three buckets going at all times; one for harvesting from a mature culture, one for starting a new culture, and one with just green water.

5. STORE YOUR DAPHNIA -- If I had too many daphnia to feed my fish, I would store them in a neat way. Fill an ice cube tray 1/2 way with water. Net out some daphnia from your culture and fill each cube in the tray the rest of the way with live daphnia, then freeze it. To feed your fish, just drop one of the cubes into your tank and voila! You have a slow-release daphnia feeder! :-)

Tips & Warnings

• Daphnia are very sensitive to pollutants. Use only clean, aged water.

Resources

• A wiki page on Daphnia
• Where to get a starter culture