I can't seem to breed Daphnia.

I have a small tank with 2 litres of water.
When I buy a bag of Daphnia (Magna?) they seem to do well for about a week, but afer that I notice a strong drop in the colony size.
I've tried feeding them yeast, but maybe I overfed the few that were left because they were all dead within 2 days and the water smelled horrible.

After completely cleaning the tank and adding fresh dechlorised water I put a new bag of Daphnia in the tank. again, the first week they looked fine, but after that the colony dropped rapidly and now there are only a handful small ones left.

Do I need to cycle the tank before I add the daphnia? I can't really do waterchanges, because when I try to suck up water, I also suck up the daphnia. And refreshing half a litre of water with a small turkey baster is just hell.

Is there also a method to separate the living ones from the dead ones when you buy them in the store?
In the bags I've bought the whole bottom of my tank is covered with bodies. Is this a problem or is this a great food source?

I've also noticed that there are a number of cyclopses in the tank.. could they be killing the daphnia?

It's kind of emberassing that I can't even breed daphnia

Breeding daphnia is not so simple, don't feel badly! Everyone fails a couple of times until they get it right. It is like balancing on top of a pole - you can fall off in many directions. Overfeed, underfeed, over-harvest, under-harvest, too clean, too dirty, too crowded,... all of these things can kill them, you have to arrive at the right balance.

It is possible that you had too many to begin with. If they are already crowded, they will not reproduce. A 2-liter container is too small, especially for D. magna. I grow them in a 60-liter tub. Yes, you should remove the dead ones from the bottom, the decay is not good. Also, you need to remove any other debris from the bottom too.

When you add yeast, is it completely dissolved in water first?

To do a partial water change, you need to harvest the daphnia + water. Do you have a brine shrimp net (or some kind of net/strainer that catches all the daphnia)? Pour half the water through the net: feed the daphnia to your newts, and throw the water away. If you don't need so many daphnia, it is better to throw them away than to let the culture be over-crowded.

I'm not sure about Cyclops. I think it's possible they could be bad for the daphnia, but I'm not sure.

When I added the yeast I took a big of water from the tank and dissolved them. Then I put them in the aquarium.
The page on Caudata Culture about Daphnia says that you can easily breed them in a 2L bottle. Is this for smaller species?
I can try if I can find the space for a bigger tank, but bigger than 20 litres is impossible I think. Is this a problem?

The page on Caudata Culture has a photo of a 2-liter bottle, but it is an illustration for hatching brine shrimp, not for daphnia. The setup shown for daphnia is a 20-liter tub. John Clare's page on daphnia (http://www.caudata.org/daphnia/) suggests a 4-gallon (20 l) tank, or a kid's plastic swimming pool.

I have read somewhere that Moina (a small daphnia) can be grown in 2-liter bottles. But you would need several bottles I think.

The other thing I would mention... I have heard that Daphnia do not like the chemical that is used to dechlorinate water. For my Daphnia, I use pond water, or water that has been aged for 1 week. (My tap water has chlorine, not chloramine.)

Good luck with your cultures!

i have a 6 litre glass jar which i culture mine in its worked really well. the trick is to get some pond mud which has the daphina eggs. and algae in it then add some plants which areate and take out toxins. i feed mine yeast