This subject has been discussed here many times, – and I think theres a lot of information if you searched forum. Also theres an article in our link section in english (look under live food articles, theres one on dafnia)
I too have for the moment given it up, its possible, but I think there are many different ways, and each person seems to find their own way in which they are able to keep the cultures for at least some time.
My own experience is that you need to be careful not to use tap water, but use aquarium water. Then lightning is important, as well as regular change of water (not tap). Then its really difficult to say what is the right amount of food, – I always use yeast, – I have tried many other things, – but yeast seems to be the one working for me.
Hay 🙂 .. well, it may be theoreticly true, but I think it will not work in this kind of setting, – a culture of dafnia will not get enough food from that, – and also, in my experience it will make it really difficult to seperate dafnia from all the hay stuff when you want to use the dafnia.
But again, – look around here, or other places on the internet, – it should be possible to find information about it.
And then of course, I think theres quite a difference between dafnia (ordinary) and moina. Moina are real difficult. What I am talking about here is Moina.
Ordinary dafnia, I have that in large containers in my garden, and I do nothing to feed or change water, – that is all done by nature and works quite well.
But moinas are a different thing