Looking Into Live Fish Food Cultures
  I have a 2 month old now and my fish raising habit is sort of suffering from too many things to do at once. It's times like these when laziness and ingenuity often come to the rescue. I've been trying to think of ways to feed fry without doing the twice daily baby brine shrimp dance. Change water, foul water with food that dies, leave alone all day while at work, come home, foul water with food that dies, etc. 
I am also assuming that fry constant graze or hunt for food items in a natural environment instead of trying to glut themselves and then starve. That would seem to promote lazy and weaker fry. Not to mention sitting in the nitrate build up which is probably the number 1 growth inhibitor for fish.  
So I started thinking a freshwater refugium might be helpful by supporting a constantly available, living food source. Googling turned up this in your FW filtration FAQ's. 
"The sad thing is that only since the internet has really taken off in the past 5-10 years has these issues been asked. And there isn't that many definitive answers. Years back I had thought of the exact same thing and being the scientific mind that I was attempted to set up a freshwater tank that mimicked my marine tanks. (seeing if I could set a tank up first, then move onto a refugium sort of idea. A sand or mud based substrate worked best in a planted aquarium (rather than any sort of gravel).  It offered a better medium for the plant roots and for microfauna to build up some colonies. 
I created mine by actually hiking into the middle of my parents woods to the stream they owned and scooped a bucket full of the sand/mud from the riverbed. I made sure that the area wasn't near any roads or field run offs so there shouldn't be that many chemicals in there. I then brought it home to add it to a tank I had set up with a bag of "Southdown Children's play sand" as substrate. I added the contents of the bucket to the tank (after looking through it for pieces of glass and things I wouldn't want in my tank). I thought that I could see if some things would colonize the remainder of the sandbed just like if you were to seed a reef tank sand bed. 
I found that it did work. Lots of little bugs were in the river bed that quickly started working away on the sand. The down side... many of the bugs found on land in freshwater are the larval stage of some sort of flying insect... (keep a lid on your tank!)"
I am a stream quality monitor and have a very basic idea of what I would get from my local stream, at least on the macroscopic level anyway. Lots of gnarly things like hellgrammites and dragonfly larvae to mention a few. The microfauna would be a good first food for many fishes, but what would they eat next to transition to adult fish food? There are smaller aquatic midges and worms, etc, but those don't seem to be as populous, at least to my naked eye. 
So as of now, I'm thinking that fry would not have a good chance of making it too adulthood. (Not that fish in the natural environment would) And I would like to better the wild survival rate and at least make enough fish to sell or trade. I am mostly interested in Angels, Corys and Bettas, but also barbs, danios, and other American cichlids. 
Is there a good source for what the fry of these fish eat in the wild? 
How can I produce that in the aquarium?
More rambling...So while I wrote this e mail, I started wondering about vernal pools, which I don't know very much about, but I do know that these pools are teeming with small insect larvae, etc. Would it be possible to recreate a still water pool in the home, without hatching tons of mosquitoes and other uglies, and produce some sort of food animal for fry that would not die and foul the water? I read something once about blue gourami breeders seeding grow out tanks with green water, then dumping a daphnia culture in, and letting the fry raise themselves, is this possible?
I'm hoping this e mail provides others with some ideas about raising fry, serious breeders really should always be looking for ways to produce better fry, in a more efficient manner. Thanks for any insights you may have, and the 12 hours it will probably take just to read all this. 
Peace,  Zach
< Feeding fry has always been a challenge for breeders since they started to breed fish. There are many ways to hatch baby brine shrimp. I suggest that you research the fish you are trying to breed and see what the breeders are feeding them. For instance if the betta breeders are feeding infusoria, then start to research infusoria. You will find many different methods and many suppliers online.-Chuck>