Daphnia As A Live Food For Aquarium Fish

What are Daphnia:

Daphnia are a very small freshwater shrimp like creatures. They are found in small pools, ditches and ponds all over the world. They thrive best where there is an abundance of food for them. They are filter feeders, that is they swim around and filter the water for smaller organisms. They eat rotifers, algae and infusoria. Serious oldtimer Aquarist used to go on collecting trips for daphnia every weekend and they considered daphnia the best fish food available. I don't advise collecting wild daphnia because of the potential of possibly bringing home diseases, parasites or other undesirables along with the daphnia.

Getting Some Daphnia

Daphnia are hardly ever avaliable in petshops, I have no idea why. But if you want to try them your best bet is to start a culture of your own. You can buy a starter culture from fellow aquarists or try a place like Aquabid.com which usually has some listed and I am currently offering starter cultures on the Stock Shop.

Culturing Daphnia


Daphnia line drawing
Looks like a scene from "Jar Wars",
but it's really a drawing of daphnia
many times larger than life.
What you need: Culturing daphnia is not the easiest thing to do. Some people seem to have excellent luck with them while another doing exactly the same procedure fails altogether. I have an old unused swimming pool that I let turn green with algae and use the greenwater to feed the daphnia. I also sometimes use yeastwater, a mixture of a small pinch of bakers yeast and a little water "all shook up" (ah hu hu). When using yeastwater add only a very tiny bit at a time, you want to just see a faint cloudiness, no more. daphnia die quicker from overfeeding than anything else. Once you start a culture it's a constant job, not hard to do but requiring constant attention. they need water changes just like aquariums. I usually accomplish this while I'm harvesting the daphnia. I siphon out about a quart of the daphnia jar thru a brineshrimp net, or the toe portion of an old ladies panty-hose (I use my old lady's usually, just another way to get her involved in the hobby). This catches a good quantity of daphnia that I can now feed to the fish. I then add a quart of greenwater or a quart of clean water and feed some yeastwater back into the daphnia jar. I advise setting up 2 or more one gallon cultures so if something goes wrong with one you'll have a backup. Of course a bigger container is better. The culture jars need to have an open airline running to them, doesn't need to be deep in the jar, just enough to keep the surface agitated and keep the water circulating around. This is very important because it keeps the daphnia food circulating around so they can eat. Don't use an airstone, they create too many fine bubbles that can stick to the daphnia, thus taking them out of circulation, and leaving it hopelessly floundering around the jar.

Close up of an adult daphnia moina
Other items I've read about (but haven't tried) that are used to feed daphnia are graham bran, alfalfa powder ( both from healthfood stores), blended spinach, liquid fry food, blood meal (yuk) and rabbit pellets. Another food I have just heard about is Gerbers Baby Food, Sweet Potatoes. It is said to be an excellent food for the daphnia with the added benefit of indirectly feeding the fish some high carotene food that will enhance their color. Other foods consisting of various manures have been suggested, but I really don't want to get into that crap.
 
One trick that I find especially pleasing is to put 10 to 20 or so adult daphnia in a fry tank. Though the daphnia are too big for the fry to eat, any baby daphnia they have will make good food, (they are smaller than baby brine shrimp) and the daphnia help keep the water clean. Of course you don't add any daphnia food to the fry tank.
 
There are several types of Daphnia commonly available. Daphnia Magna is about the biggest (about Brineshrimp size), followed by Daphnia Pulex a little smaller, and then Daphnia Moina, the smallest. I prefer the Moina because they are happy in water that is around room temperature, 70 to 85 F, (it's HOT in Alabama) while the other species require lower temperature, around 55 to 68F.
 
All species will do great outdoors in the warmer months. I use a kids swimming pool. Just throw in a handful of plant food fertilizer to get the pool green with algae first and then add the daphnia a few days later.
 
Daphnia Moina in a gallon jar
One of my Daphnia Moina culture jars, right after feeding yeastwater.
Note that you just want a slight haziness.
Notice the airline tubing, and yes that is a snail, doesn't hurt a thing.
Also adding a little marine type aquarium gravel or oyster shell will give
the daphnia a buffer from a low pH and supply them with needed calcium.

 
UPDATE:
I have read that it's not good to keep the lights on a daphnia culture all the time, but as a constant experimenter, I tried it anyway. The results were outstanding, the daphnia have doubled to tripled their production. I've been doing this for 2 months now, so there has to have been several generations raised in constant light. So far there are no bad side effects, other than having to feed the daphnia everyday as opposed to once every 3 days before. I am currently using a 10 gallon tank with an old incadescant aquarium light fixture. I feed the daphnia about an 1/8 teaspoon of bakers yeast a day, and harvest about a 1/4 to 1/2 teaspoon of daphnia a day, everyday! Also in the tank are 100's of snails and I throw them a small leaf of lettuce every few days. An added benefit to the constant light is that the fish now have a night light, and I put microworm cultures on top of the light, the heat makes the microworms multiply and grow much faster.
 
See Also
 
Live Food For Aquarium Fish - An Overview
Brine Shrimp - A Popular Fry Food
Micro-Worms - An Easy And Prolific Food For Fry
Grindal Worms - Fishes Favorite
Infusoria - For The Very Tiny Fry
Mosquito Larvae - Grow Your Own Fish Food
Vinegar Eels - Very Easy to culture
Live Foods available from Petfish.net