Daphnia 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!
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!
Love these are more nutritious than brine shrimp, would be fun to breed them as an on hand sw aquarium food!
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.
Always thinking
thank you for this great info
Great read. Live food is critically important to the health of any ecosystem. I love the foods i get from the barn!
I never thought about feeding my fish these before. Good to know I can!
Right? Me too!
Interesting!
I always though daphnia were like the celery of fish food, but I was wrong.
I’ve never grown love food fish, but after reading this article, I am willing to give it a try.
Do these breed in the fuge?
We’ve always used brine shrimp and this is a first hearing of Daphnia. I guess you learn something new everyday!!!
Live food is best in my opinion
I wish I knew about Daphnis earlier. They are awesome super foods
I might have to try these one day. I am always up for a new treat for my piece of the reef.
Great read
Good info
It’s a forever food. They breed in your tank!
Great food have not had a problem 😀
might have to try some daphnia
might have to try some daphnia sometime, great write up
the more i read the more i learn!!!
Interesting read, but the thought of them make me itch LOL
interesting read
Awesome information
Very interesting
going to have to try these
A varied diet can’t help but make your fish, and maybe corals (?), healthier and more vibrant!
I’m feeling itchy. I guess one negative is not being able to pour in and continue populating.
I love adding this food source to my tank just to add some variety in diet. 10/10 for the sea flea
Awesome
Awesome
I have not heard of these before. Good read, and educational
Great article, thanks for the information.
Seems like a lot of work to be able to support feeding at home over a long period of time.
roll em out
Definitely will have to try them!
Once again very educational and interesting blog
Great article. I never considered Daphnia as a supplement. I am seriously considering implementing such a culture in the future.
Lots of work but worth it
Very interesting.
Great read! Thank you Algae Barn!
Can’t wait to try this with my mandarin
Totally worth the expense in my opinion
My fish would love them
Would this be good food for a Mandarin?
Great information. I may have to try!
Good info!
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.
I love learning about new diet supplements to feed my reef and this was a great find
Great info thank you.
Enjoyed the topic and informative in helping me with a successful reef tank (Y)
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…
I have used the daphnia in a jar but never live. I would love to try them.
I had not heard of daphnia before.
I need to learn how to grow these!!
Cool
so awesome
Thank you for posting this!
😀😀
What type of fish are these good for
What are these best for
Awesome
Super interesting! I have seahorses and will try this as a treat!
so much information! Thank you!
I had no idea
How informative .. and useful!
I’ve used these in lab in college! Love learning more about them!
Not too shure if i should add these along with copepods.
One of my favourite things about this hobby is how much there is to learn. Very informative!
Hmmm, interesting option. Something to consider down the road.
Hmmm, interesting option. Something to consider down the road.
Always great info in your articles
Another helpful article. Thanks for the info.
Thanks for the great read
Thanks for the info
So alien like
Great idea for love food
A bit of a hassle but definitely worth it in the end.
Very Informative!
Thank you for posting this!
Haven’t try it but I’m going to give it a try one day
I used mine to feed both my freshwater and saltwater set ups!
Even my bettas loved them!
Interesting read
I’ve got pods in my tank and they are a great addition. May have to give these guys a try next.
Very interesting
Interesting. Going to have to look more into this.
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
I will have to give this a try. Have used it for my freshwater fish for years.
Will have to giv this a try for sure!
Will have to try this for sure!
Great information. Thanks for sharing
Going to try this myself! Great alternative
Very good info
thanks for the info!
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.
Never would have considered using “water fleas” as food for my aquarium fish. Learn something new every day.
Definitely know your tank is established when you start seeing these little critters everywhere.
Definitely know your tank is established when you start seeing these little critters everywhere.