Raising Daphnia for Tropical Fish Food

by Glen Thode

Daphnia is a highly nutritious, live food that you can easily raise to feed your tropical fish. Daphnia are also know as “water fleas” because of the way they jerk and move while swimming through the water. Daphnia are small, fresh water crustaceans that can be found all over the world in freshwater lakes, streams and ponds. They are an excellent source of fish food due to their high protein content. We feed lots of daphnia to our discus, especially the young fry(1/4 inch to 3 inch size).

Growing Daphnia Tips

You can grow daphnia in almost any type of container. We grow them in concrete vats in our greenhouse. If you need a lot of daphnia, it's best to use a container that has a large surface area(a large plastic tub, 40 gallon aquarium or a kiddie swimming pool). If you don't need a lot of daphnia, you can also raise them in a 1 gallon glass jar, 3 liter soda bottle or 10 gallon aquarium.
Always age the water in your container before adding the live daphnia culture. Daphnia does not tolerate chlorine. It will usually die if you add tap water directly into your container when making water changes.

We age the replacement water for 10 to 14 days in the tubs above the daphnia vats.
The water will turn green with algae and provides some food for our daphnia when we do a water change.

The pH of the water can range from 6.2 to 8.9 . We usually keep the pH of our water at around 7.8.
Change 20% of the water at least every 2 weeks. Remember to use aged water as your replacement water. You can even use your old aquarium water, when you do a water change, as replacement water. If your daphnia culture is not reproducing quickly and thriving, you might want to do more frequent water changes.
The ideal temperature for growing daphnia is usually 72 to 85 degrees. When the water gets too warm, the daphnia culture will stop reproducing.
The daphnia culture doesn't need much oxygen to thrive. Containers kept outside with a large surface area don't need any aeration at all. Containers kept inside should have very light aeration(just enough to break the water surface). Too much aeration(bubbles) can kill off your culture.

It's a good idea to have multiple containers of daphnia growing at the same time. Having a backup culture is great insurance if a daphnia culture goes bad and dies.
Keep your daphnia containers in the sunshine. 6 to 8 hours of lighting is best. You must have a light on your daphnia for at least 10 hours if you grow them indoors. Placing their container in a sunny window is also a good idea as long as the water doesn't get too hot.
Daphnia will eat algae(green water), yeast and bacteria. We feed our daphnia yeast. We put yeast powder into a bucket with water and mix it. We then add enough of the yeast mixture to our daphnia container so that the water is slightly cloudy. The daphnia are filter feeders and will eat the yeast in the water. We feed the daphnia whenever the water becomes clear. Do not overfeed.

Live daphnia harvested from our vats.

We use a fine net to catch our daphnia. It's best to move the net in a slow figure 8 motion when trying to catch them. We then sift the daphnia through several different size strainers. The larger size daphnia is fed to the larger size discus. The smallest daphnia is fed to the tiny discus fry.
Finding daphnia starter cultures should not be that difficult. Check the classified ads in tropical fish magazines or ask members at your local fish clubs or on tropical fish forums to supply you with some.
It's important to harvest your daphnia on a regular basis. Failure to do so can cause the culture to crash due to overcrowding.

Live daphnia is a great food source for your tropical fish. We highly recommend it if you are raising small discus. It's very easy to grow if you follow the tips above. Your fish will love eating it.