Daphnia Culturing for Use in the Home Freshwater Aquarium written by Bryan Cetroni, West Chester University Abstract: In this article, I go into the benefits of live food for fish. Food types for daphnia will be brought up, also along with ways to culture them. Various set ups for culturing these creatures will also be brought up. Fish and Invertebrate nutrition is always quite important when dealing with what kind of food to use. The main types of food used in the trade are flakes, sinking/bottom feeder pellets/discs, freeze dried, frozen and live. Each has its positives and negatives; however we will deal with the last one. Live food is usually the least used, especially in areas where most LFS only sell feeder fish. Live food stimulates the natural predator behavior of fish. From personal experience, I have found that my fish are much more active and even seem healthier when they have something that mimics what they would eat in their natural environment. Live foods also are a great way to condition fish into optimal breeding condition. After starting a regiment of Black Worms, I caused my Albino Corydoras start to spawn. Now there are many different kinds of live food that can be used. To name a few there are micro worms, brine shrimp, red worms, mosquito larvae, wingless fruit flies, various worms and daphnia. Now I have used most of these, and also done research on using these and find that there are inherent problems with many of them. The medium I found for fruit flies used mayonnaise and molasses (Fish Lore). This medium can start to smell real bad. Also, if fruit flies escape, even wingless variants can easily start to reproduce like crazy. Mosquito larvae are only good for warm weather since, as I discovered, trying to rear them indoors becomes quite difficult since they usually end up escaping and proceeding to attack the mammals of the house. Brine shrimp are great, although since they are saltwater they will die due to lyses in their cells because of the difference in water concentrations. This gives them a short lifeline than freshwater foods. Worms are good, although my experiences with raising Black Worms have led to slow growing colonies that more often than not end of smelling quite terrible. However, no we reach the subject of my paper, Daphnia Magna, the water flea. Since I culture Daphnia Magna, I will talk about culturing them. There are other Daphnia breeds that can be cultured; however the basic culturing is the same for all of them. The Daphnia Magna, or water flea, is a small freshwater crustacean. They get their name from the jerky, flea-like movements that propel them through the water. They are filter-feeders, which mean they eat microscopic organisms in the water. They reproduce through pathogenesis, which means that no males exist, only females. The young are clones of the parents. I will not go in depth on the biology behind them, but will include a link that goes more in depth with them. Now I will go onto how to culture these little guys in a manner that is efficient and effective. They are very similar to brine shrimp in culturing methods, except these are with freshwater. I will start with my first attempts to culture these. Daphnia-Culture Mark 1 consisted of three 5 gallon buckets picked up at the local hardware store. The main bucket has the daphnia, and the others were used to culture greenwater. Greenwater is a good food choice for daphnia, and I will get into these at a later point in time when I get onto feeding them. This worked great, however the lack of water movement caused a film to build up, and water changing was quite difficult. Eventually the entire culture crashed, so I waited a while and then restarted. Mark 2 consisted of a 10 gallon aquarium that I had found in the garbage (along with the Reptilian inhabitant that had no survived too well =( ). I fixed a small crack in it, and filled it up with water. I then used a sponge filter attached to an air pump. This solved many of the problems that Mark 1 had, and kept the water clean and oxygenated. As of now this tank grows them quite well. I also added a CF light bulb attached to an old gecko-lamp. This was brought up as an idea to help them culture better, and it has. A hypothesis why will be brought up later with food culturing. Mark 3 is already in the makings and will be a seasonal way to mass produce millions. I have a slightly opaque 55 gallon barrel that is being converted into a rain barrel in order to conserve rainwater. I plan on using it to culture Greenwater, then seed with daphnia. The results should be massive amounts of Daphnia. Now that I have mentioned it multiple times, you probably ask what Greenwater is. Greenwater is a microalga that grows in the water column, causing the water to become light to dark green in color. Many fish keeps see this as a nuisance; but Daphnia love it. This is some of the best stuff to feed your daphnia. The recipe I use is old tank water from water changes, which then has Organic Miracle Grow added to it at a concentration of 1 tsp per gallon of water. This water is then placed in buckets, or empty 2L soda bottles. Airlines can be run into the soda bottles to keep algae build up off the sides but usually that does not seem to be a problem with me. A note of caution if culturing greenwater outside: cover your buckets. Otherwise you will end up with other creatures that like greenwater, and some creatures that like to eat daphnia. The green water should be fed daily. I originally started Mark 2 with greenwater in their tank, and it helped keep them growing longer. Other types of food for daphnia are yeast and bacteria. Yeast is a simple way to feed them, I use it when my greenwater stores run low. Just take approximately ¼ tsp of dry Active Yeast and dissolve in fish tank water. Then pour into the Daphnia tank. Do not use this too much, since this could destroy water quality causing the Daphnia to die. The other type of food is bacteria, which should be left to outside cultures. This bacteria is made by taking dried horse or rabbit droppings and putting them into a pair of pantyhose, and then floating them in the water. Again this should be for outdoor use only. Gutloading with Spirulina is also advisable right before you feed them to your fish. As far as weekly maintenance goes, do the water changes at the same time as you do the water changes in your fish tank. Just change a quarter of the water every time you do a water change. Daphnia can be very sensitive to water chemistry so too much ammonia can cause them to die. While suctioning out the tank you can attach pantyhose onto the end of the gravel vac. This makes harvesting and cleaning the same job. A big problem with culturing daphnia is keeping population in control. If the population density gets too large, it will cause the water to foul and water chemistry to crash. That can ultimately lead in the death of your culture. So it is advisable to try to harvest daily, especially with larger set ups. If you do by chance forgot to harvest and the tank crashes, do not fear. When water colonies go down Daphnia will change their reproducing habits. They will start to create eggs, that will be shed with their shells. So if your colony dies, then let the tank dry out. Refill with tank water and you should be good to go. That should be everything. Feel free to question me about this article. I give a lot of credit to John Clare of Caudata.org, since without his article I would not have had much data. He goes into the biology a little bit more in depth. Works Cited Clare, John. “Daphnia”. www.caudata.org/daphnia/. August 1998, December 1999, May 2000, March 2001, July 2002. FishLore. Fishlore.com. For more information go to either www.caudata.org/daphnia/ or feel free to contact me.