Daphnia as a Live Marine Aquarium Food by Kenneth WingerterDaphnia sp., widely known as water fleas, are hardly new to the aquarium scene. Freshwater aquarists (and perhaps quite a few saltwater aquarists too) have scooped them from ponds, ditches, etc. to use as aquarium feed for at least a century. Some particularly assiduous hobbyists have even found success culturing these tiny crustaceans for long periods of time by feeding them homemade green water. And perhaps a little yeast… And a little of this, and that… The effort of cultivating these creatures, however laborious, has proven worthwhile to many serious aquarists (especially fish breeders). The reason for this is simple: Daphnia are extremely nutritious and fish love them. Still, for those who just don’t have the time to raise their own (or to wade into the nearest waterhole with a dip net every weekend), obtaining inexpensive, fresh, live daphnia has been frustratingly difficult. AlgaeBarn has changed all of that with the commercial-scale production of Daphnia magna. For those who aren’t yet all that familiar with the water fleas, these are big ones. Actually, at a length of up to 5 mm, they’re about two or three times as large as the average daphniid. This makes them a bona fide community fish food. While not too big for some corals (mainly LPS), they are certainly large enough for a considerable variety of reef fishes to capture and consume. Their slow, conspicuous (sort of daft, to be honest) swimming movements make them a sure target for any zooplanktivorous reef fish in particular. An exotic delicacy Alright, so if you do know much about water fleas, you’re already aware that they’re not from coral reefs. Neither are brine shrimp, but brine shrimp nevertheless have kind of proven to be an awesome reef aquarium food, right? Same here. Like adult brine shrimp, Daphnia magna are relatively huge pods that exhibit a “tempting” swimming behavior and are easy for predators to catch. But unlike unenriched adult brine shrimp, Daphnia magna are absolutely loaded with nutrition. This all makes them really, really useful for a couple of purposes. Firstly, they are very effective for prompting sick or unusually finicky fish (e.g. tilefish) to resume feeding. While easily noticed, and apparently very alluring, they are effortlessly captured even by slow, ill or shy fish. They are just as easily consumed, as they cannot put up much of a fight going down. Secondly, they are highly useful as a supplemental live food item. Of course, the diet of the food organism affects its nutritional content. But daphniids are generally quite wholesome regardless of what food they’re raised on; at around 45-70% protein and 11-27% fats/oils, they’re not too shabby as far as pod nutritional content goes. And their larger size all but guarantees that most, if not all, of your reef fish get a few big bites. While we stress that these are definitely great as a “treat” for the typically diverse reef fish community, they’re downright amazing for enhancing the diet of more dedicated zooplanktivores like seahorses, pipefishes, anthias, Genicanthus angelfish, large mandarins, etc. Portion control The key to using this particular pod is feeding it out slowly. The reason for this is that it cannot survive for very long in full-strength seawater. Luckily, it is adapted to slightly brackish environments (up to 8 ppt) and can tolerate reef conditions for a short while. Adding just a few at a time ensures that each gets eaten while still hanging openly in the water column. This is especially important for strongly zooplanktivorous types of fish such as seahorses. One cool thing about these Daphnia magna is that they are raised in brackish conditions and are pre-adapted as much as possible to the salty waters of your reef system. If you wish to feed them out very slowly, you can simply hold them in a gallon or two of dechlorinated tap water (unheated and lightly aerated) with a very small amount of salt (just a few parts per thousand). To maintain their health and nutritional value over longer periods of time, we recommend feeding them while they are in holding. Like other daphnia, they eat a wide variety of tiny things ranging from phytoplankton, bacterioplankton, detritus, protozoans, and so on. AlgaeBarn recommends feeding them with what they feed them: A base diet of OceanMagik (for protein, fatty acids, carotenoids) with a dash of PNS YelloSno (for yet more protein as well as vitamin B12). While daphnia reproduction is a bit on the slow side (just a few individual young per clutch!), they persist for quite a while under basic culture conditions. They are not particularly demanding, but certainly live longer and at higher densities when conditions are relatively stable. Daphnia magna has an average lifespan of ~40 days at 25°C and ~56 days at 20°C. Give them frequent but small feedings of high quality food (preferably a B vitamin-rich diet based on live phytoplankton) and refresh their culture water often (30-50% changes every day or so). A source of bright illumination (12-14 hours/day) helps to keep live phyto (if used) alive. You’ll probably notice that they do consume their food very quickly. Despite this, do not be tempted to overfeed; foul water will ruin a culture in very short time. Those with large, well-stocked reef systems won’t need to bother with holding. That’s for sure! In those cases, a whole portion of these daphnia can be added at once, as the fish won’t rest until every individual is consumed. You might even be surprised by the ferocity with which fish attack these big, juicy pods. Even if your fish are spoiled with regular additions of live brine shrimp, they’ll still go nuts when they see daphnia hit the water. We’re honestly not sure if it’s their beefiness, the way they swim or their nutritional content that consistently drive fish so wild–we’re just stoked that they work so well!
Thereasa Gardner says July 20, 2020 at 1:18 pm I’d love to try all assortment of live foods. I’ve been growing copepods and amphipods in my tank, and theyve been doing great! Reply
Shawn Vest says July 20, 2020 at 1:27 pm Love these are more nutritious than brine shrimp, would be fun to breed them as an on hand sw aquarium food! Reply
Russell George says July 20, 2020 at 1:30 pm Sounds weird bringing fleas into your house but if the fish love them, it may be a good treat for them from time to time. Reply
Richard M Jackson says July 20, 2020 at 1:50 pm Great read. Live food is critically important to the health of any ecosystem. I love the foods i get from the barn! Reply
Christalyn Maza says July 23, 2020 at 8:38 am I never thought about feeding my fish these before. Good to know I can! Reply
Peter G says July 20, 2020 at 1:47 pm I always though daphnia were like the celery of fish food, but I was wrong. Reply
jugheadmckinney says July 20, 2020 at 1:52 pm I’ve never grown love food fish, but after reading this article, I am willing to give it a try. Reply
Joy Chadwick says July 20, 2020 at 2:07 pm We’ve always used brine shrimp and this is a first hearing of Daphnia. I guess you learn something new everyday!!! Reply
Octavio V says July 20, 2020 at 2:32 pm I wish I knew about Daphnis earlier. They are awesome super foods Reply
Jeremy says July 20, 2020 at 2:52 pm I might have to try these one day. I am always up for a new treat for my piece of the reef. Reply
CHRISTIAN DOMINE says July 20, 2020 at 3:54 pm might have to try some daphnia sometime, great write up Reply
Kayla Lussier says July 20, 2020 at 4:17 pm Interesting read, but the thought of them make me itch LOL Reply
scotty8284 says July 20, 2020 at 6:36 pm A varied diet can’t help but make your fish, and maybe corals (?), healthier and more vibrant! Reply
Steven Flores says July 20, 2020 at 6:38 pm I’m feeling itchy. I guess one negative is not being able to pour in and continue populating. Reply
Ethan says July 20, 2020 at 7:18 pm I love adding this food source to my tank just to add some variety in diet. 10/10 for the sea flea Reply
Frank Politi says July 20, 2020 at 8:18 pm I have not heard of these before. Good read, and educational Reply
Brandon Baumann says July 20, 2020 at 9:44 pm Seems like a lot of work to be able to support feeding at home over a long period of time. Reply
Robert says July 21, 2020 at 7:43 am Great article. I never considered Daphnia as a supplement. I am seriously considering implementing such a culture in the future. Reply
Bob & Brenda Gardner says July 22, 2020 at 5:36 am I have always been reluctant to feed anything to my aquarium that is not naturally found in the ocean. I will need to give this some thought, just maybe I will try it. Reply
zadok jollie says July 22, 2020 at 8:36 am I love learning about new diet supplements to feed my reef and this was a great find Reply
John Solomon says July 22, 2020 at 10:24 am Enjoyed the topic and informative in helping me with a successful reef tank (Y) Reply
justan jenkins says July 22, 2020 at 7:25 pm Hmm well i do have a freshwater aquarium… i wonder if mollies would eat them or let them live in peace to multiply for a future saltwater tank… Reply
Scott D Carpenter says July 23, 2020 at 2:08 am I have used the daphnia in a jar but never live. I would love to try them. Reply
Catherine Carreiro says July 26, 2020 at 12:15 pm Super interesting! I have seahorses and will try this as a treat! Reply
eve.roberts2024 says July 26, 2020 at 11:57 pm I’ve used these in lab in college! Love learning more about them! Reply
Juan Carlos Perez says July 27, 2020 at 11:29 am Not too shure if i should add these along with copepods. Reply
smithma274 says July 27, 2020 at 2:25 pm One of my favourite things about this hobby is how much there is to learn. Very informative! Reply
Grace Riley says July 27, 2020 at 2:33 pm Hmmm, interesting option. Something to consider down the road. Reply
Grace Riley says July 27, 2020 at 2:33 pm Hmmm, interesting option. Something to consider down the road. Reply
Cynthia Taylor says July 28, 2020 at 9:19 pm I used mine to feed both my freshwater and saltwater set ups! Even my bettas loved them! Reply
ROBERT FERNETTE says July 29, 2020 at 12:46 pm I’ve got pods in my tank and they are a great addition. May have to give these guys a try next. Reply
Shannon Pickin says July 29, 2020 at 8:10 pm Interesting. Going to have to look more into this. Reply
Debra Hayson says July 30, 2020 at 1:55 pm I have never heard of this brand of food for fish and I haven’t had a fish aquarium in years would like to try having fish again Reply
Richard Hicks says July 30, 2020 at 2:37 pm I will have to give this a try. Have used it for my freshwater fish for years. Reply
Kale says July 31, 2020 at 7:49 am It’s brilliant that these are raised in brackish conditions. I’m wondering if all dahlia can be raised that way or just certain species. Reply
Rudy A Garcia says July 31, 2020 at 2:58 pm Never would have considered using “water fleas” as food for my aquarium fish. Learn something new every day. Reply
kirkbovie says July 31, 2020 at 4:07 pm Definitely know your tank is established when you start seeing these little critters everywhere. Reply
kirkbovie says July 31, 2020 at 4:07 pm Definitely know your tank is established when you start seeing these little critters everywhere. Reply
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