The benefits of feeding live food to fish in a community tank are many: live food will improve vigor and color, and more closely resemble the food found in the fish's natural habitat. Live food is easily obtained.
Some drawbacks include the transmission of diseases or parasites to the aquarium, it is time consuming to maintain the cultures, and a lot of space needs to be devoted to raising live foods. The cost of equipment and supplies needed to maintain cultures is also a consideration for the beginner.
In this article I will discuss how to raise Daphnia. This article will be part of an on-going series on live foods. You can find many more related articles at http://www.kingdiscus.com.
Daphnia belong to a group known as the Daphniidae, and are close relatives of the freshwater shrimp, and the brine shrimp (Artemia). Their generic name is generally referred to as "water flea." This common name is derived from the jerky movements of Daphnia in the water. The over 150 different species can be found in North America, with a similar amount of species growing in Europe. Some of these species find common ground on both continents.
Daphnia are a small crustacean, and are great to use as a fresh food because they will exist in the tank water until eaten by the fish. Daphnia can also be sterilized if it is felt necessary by placing in a 5% solution of Clorox for 3 to 5 minutes. Very few micro-organisms can survive this. Be sure, however, to rinse them thoroughly before feeding!
Daphnia can be raised both indoors and outside. Many people raise daphnia in a small children's wading pool. A more controlled environment, however, is done indoors, and can be done year round if one lives in northern climes. This can be as simple as a couple of two liter bottles, to a 20 gallon tub purchased from a store such as Menard's. The ideal situation is to have as much oxygenated surface area as possible, so if there is room for a larger container, by all means use it. A shallower environment suits daphnia best for prolific growth.
Setting up the environment for daphnia is quite simple. Many methods are used for collecting the water to use for the culture. The best advice I have heard is from Joe F. of Circle City Aquarium Club in Indianapolis, IN. He gave a presentation at the August meeting of Southwestern Michigan Aquarium Society, and recommends using tank water saved from a tank change. Joe has been raising live foods for a long time, and has had good success. His video presentation was top notch.
PH levels for successful Daphnia cultures should be in the range of 6-8, and should be more alkaline than acidic. If raised outdoors, no aeration is needed. If raised indoors, aeration should be adjusted to produce large bubbles. Small bubbles in the daphnia culture will cause the bubbles to become lodged in the carapace of the culture, and they will die.
Water temperatures for Daphnia magna are not a high requirement, but the optimal temperature should be in the 64-72 degree range. they are very tolerant to changes in temperature, and can withstand fluctuations down to freezing. In fact, Daphnia can be frozen and kept in the freezer, and then revived when needed. Moina withstand a higher fluctuation in temperature than do D. magna.
Lighting should be in the neighborhood of eight or more hours light per day and light intensity equal to or greater than 850 lux. A simple light and a timer can accomplish this indoors.
Feeding the Daphnia is where most aquarists fail. Daphnia feed on dissolved organic matter, yeast, various groups of bacteria, microalgae, and detritus, or mulm. Organic fertilizers, such as fresh cow manure. It is not recommended by our breeder, though, because of the antibiotics and supplements fed to dairy and beef cattle. A much better mixture is a combination of one tablespoon each of spirulina, soy flour, and active dry yeast, added to a pint of water. This mixture should be added so that the water is cloudy, but you are able to see the bottom clearly, and observe the Daphnia swimming in the culture. This mixture should be added carefully every two or three days, being careful not to over feed. At this time, you should see an abundance of Daphnia, and they can be harvested to feed your fish.
Harvesting is quite simple - simply use a small aquarium net, observing that the smaller Daphnia fall through the netting to grow further. In this way, the adults are harvested, and can be fed to your fish. The younger Daphnia can go on to produce still more fish food. Harvested Daphnia can be kept in the refrigerator for several days in clean water.
Daphnia are high in protein, and a very good diet for tropical fish. Some aquarists feed them exclusively. They provide up to 70% protein to your tropical fish, and are an excellent source of live food for the aquarium.
Much can be written on the culturing of Daphnia. This guide is only meant to help the beginner to live foods to establish a colony, and feed live food high in protein to their fish. A series of article on live foods is forthcoming, and can be viewed at http://www.kingdiscus.com.
Alden Smith is a published author, and has been marketing on the internet for 7 years. Read more articles at his website, King Discus, an active gathering place for discus breeders and lovers of discus fish. His wife Betsy is the administrator of All The Best Recipes a site rich in free online recipes and cookbooks.