Culturing Daphnia and related species
By Jim Langhammer The subject "Daphnia" is used by aquarists in a very imprecise application and questions are asked that verge on "how do you maintain a fish"? Many aquarists think all "water fleas" are a species of the genus Daphnia. NOT TRUE! When you collect "plankton" you may get many related crustaceans called cladocerans, which are close relatives of Daphnia (plus ostracods, copepods, insect larvae, fairy shrimp , etc.). In order for meaningful communication and comparison to be accomplished, we need to level the playing field. The many "water fleas" have very different requirements from one another and generalizations are not possible!

My comments refer ONLY to the colony commonly referred to as Giant Russian Daphnia (tentatively IDed as Daphnia magna) which was brought from Moscow in approximately 1960 by my friend George Campbell. I received the colony from George in 1963 and have distributed it widely since then. George used the daphnia to "sweeten" the water in his basement alligator pool and harvested daphnia to feed his fishes!

This colony has for 40 years been consistently propagated at approximately 70 degrees F. and has apparently lost its ability to enter a sexual stage and produce resting eggs when stressed. I have occasionally heard reports that if pond-reared outdoors it has reverted to resting eggs during the Winter. The fishroom reproduction is accomplished by parthenogenetic females.

This Daphnia and most cladocerans require high levels of dissolved oxygen and warm water rapidly loses its ability to carry the required level of oxygen as the temp increases. This is why Daphnia and trout and other "cold-water" creatures suffocate at higher temperatures. The Giant Russian Daphnia probably will do poorly or even die out if you cannot keep the colonies YEAR-ROUND well below 80 degrees F.! (If you know that will be a problem, try culturing the small Japanese cladoceran Moina which is popular with killie-keepers. It can tolerate temps into the 80's but does not seem to like cooler waters!)

The continuing thread through most discussions of Daphnia and live-foods in general is "why bother?" and "I have no space". Quite simply if you do not have room and time in your fish set-up to accommodate something that will benefit your prized fishes, then choices must be made! I strongly urge you to empty fishes out of one or more of your coolest tanks and start cultures of the Giant Russian Daphnia. Your remaining fishes will prosper and you may even find considerable economy involved now that brine shrimp eggs are so pricey!

Once you have opted to make space available, your time becomes important. You will need to treat a HEALTHY, HIGH-PRODUCTIVITY Daphnia culture as "lovingly" as you would your most prized fishes! You frequently see a bucket of green water on a porch or a jar of daphnia on a window sill from which an occasional harvest of daphnia can be secured. By contrast, a good established 20 gallon tank can give you about 1-2 cups of drained daphnia a week!

The Giant Russian Daphnia can not only be a good source of protein and a stimulant to the natural behavior of predatory fishes but it can be a great carrier for the color-enhancing carotenoids so important to achieving natural color in tank-raised fishes. Plants are the original sources of pigments such as carotenoids and xanthophylls but fishes are unable to utilize these coloring agents until the chemistry has been altered - usually by an invertebrate. Insects and crustaceans convert the plant pigments into useable combinations. The Daphnia are fully capable of metabolizing paprika, spirulina, marigold petals, carrot oils and other carotenoid-rich foods into their own bodies so that the Daphnia become "secret" color foods to dazzle your friends by how great your fishes look!

Now comes the work! and the reason few aquarists succeed with cladocerans in general. Most aquarists do not give their fishes good husbandry and the Daphnia are far less "forgiving" than the fishes! If you rate yourself as a lazy aquarist, no need reading further.

The Steps to Success:

1. Find a culture of the Giant Russian Daphnia.

2. To an EMPTY aquarium or container (always avoid plastics!), pour in the starter culture as you received it. If the volume is small, tip the tank up so the culture water pools at one end. Beginning immediately and every few hours thereafter add approximately the same volume of aged water from a room-temperature tank in your set-up. For example: if the original culture was a pint, add a pint now making a quart of culture. Next add a quart, to become a half-gallon; etc. As soon as the water is deep enough level the tank and add an air-stone for good aeration at ALL times! Daphnia are commonly used as bio-assay organisms in laboratories because they are very sensitive to changes in water properties - chemical toxicity leaching from plastics can kill cultures attempted in garbage cans, abrupt temperature or pH shock during water changes can be lethal. Try to provide a consistent stable physical environment for the colony.

3. Daphnia should have 24 hours of light so install at least a low wattage bulb above the tank. They are strongly phototropic and quickly swarm to a concentation where the light is brightest. If a darkened fishroom is illuminated slowly by sunrise for example, the Daphnia will often crowd so densely into a corner or side of a tank near the light source that they smother themselves much as frightened chickens are known to do in a corner. The Daphnias' positive phototropism seems to override the suffocation syndrome!

4. As the Daphnia culture grows you will quickly have a concentration of organisms producing waste products, pheromones, and metabolites that will suppress reproduction and eventually poison the culture. WATER CHANGES ARE AS IMPORTANT TO THE DAPHNIA AS TO ANY FISH YOU KEEP! I change water on my four Daphnia tanks - 70% EVERY DAY! This is not preferential treatment for the Daphnia since I do similar water changes every day on many of my fish tanks which contain high densities of immature fish! How you accomplish these changes can be left to your own ingenuity. Siphoning the water out from within a "cage" of fine nylon mesh wll work. You can siphon the water into a jar, and then pour the contents through a standard brine shrimp net to harvest any daphnia for feeding. I use a very fine-meshed commercial suction strainer available through Grainger's - a nation-wide electrical supply wholesaler. Replenish the water from a source of room-temperature water. I have 55-gallon storage units of aged water and automated pumps to facilitate my water changes but those are not requisites to culturing Daphnia!

5. FEEDING KILLS MOST DAPHNIA CULTURES! Daphnia are so sensitive to low-oxygen levels and equally to high-carbon-dioxide levels that feeding too much often suffocates a colony in just a few hours time. Most aquarists feed active dry-powdered yeast to daphnia and it can be an excellent permanent diet BUT BEWARE! it is a living culture and a slight pinch too much can result in a "bloom" of yeast that suffocates the Daphnia! Learn to feed yeast a TINY portion at a time until you can accurately estimate how much yeast is consumed in 24 hours! IF YOUR WATER IS EVEN SLIGHTLY MURKY (OPAQUE) AFTER 24 HOURS, DO NOT FEED AGAIN UNTIL THE WATER IS CRYSTAL CLEAR! Few Daphnia cultures starve to death but ALMOST ALL STARTER COLONIES ARE KILLED BY EXCESS FOOD! I usually feed yeast about five days a week and the following cereal formula every three to four days.

6. Most of you will be disinterested in the work load already outlined but if you want to supplement the Daphnia for color-feeding, once or twice a week add a small amount of the following formula to the tank but NEVER ON THE SAME DAY YOU USED YEAST! Add equal parts of soy flour and whole wheat flour to make a cereal base balanced for the amino acids. Buy the reddest paprika you can find and add one part of paprika to nine parts of the cereal base. If you have any spirulina powder, astaxanthin, or other respected coloring enhancers, add a small amount to the formula - and mix it thoroughly. It stores well at room temperature but try not to make supplies too far ahead of usage date.

7. Using the afore-described formula, not only enhances the Daphnia's nutritional value but will allow you to create additional "multi-dimensional" cultures. With the cereal base I am also able to culture amphipods, copepods, and a "water worm" (Dero sp.: Annelida) all cohabiting successfully with no additional work for me. The "water worms" form mats across the floor of the culture and give me a disease-free substitute for the popular "black-worms" (Limnodrilus sp.) and the now disfavored tubifex worms (Tubifex sp.).

8. Don't try to cut corners! These are my "secrets" - give your Daphnia cultures TLC and they'll give you a resounding return on the successes you see in your fish room.

Happy Holidays to all!

Jim Langhammer

I've raised Daphnia and Moena a few times but they don't thive on the periodic neglect that say, whiteworms do so they're seldom a staple around here.

One time I raised them in 7 two-gallon aquariums. One culture was always new, one was ramping up, one was clogged with food, one was starting to crash, one needed attention rel soon now - you get the picture.

The best I ever saw daphnia do in culture was a 20 gallon tank with no fish, just lots of plants, that had gone very pea soupy green. I put some daphnia in there and in a couple of weeks the water was crystal clear - and FULL of daphnia. I threw in a couple of Endlers livebearers and the daphnia didn't last long. And I had LOTS of Endlers after that.

I consider green water the only viable food for long term Daphnia culture. Everything else I've tried has been a disaster.

Richard Sexton