Andrew the things that you are most likely refering to are the humble
Euglena. A protist that is both auto and heterotrophic, it makes a great
food for the first week or so for rainbow fry. It is also pretty easy to
culture and also easy to obtain a culture of. Southern Biological
services is where I got my culture from for $12 including postage.
I would love to try out some of the rotifers for some of the harder to
raise fry eg incisus(I have heard), many of the little gudgeons
(especially bikolanus). There is something else that I would love to try
as well, has anybody ever tried using Chlamydomonas reinhardtii as a
first food for things like empire gudgeons, bikolanus etc. It is an
extremely small motile green algae and should be perfect for those
species listed above. It is only about 1 micron across (1/1000th of a mm)
and because it swims it should get a good feeding
response. I can get the cultures of this easy enough (Again
southern biol although ANU has it and that is where I would get it from),
but I am going to leave the country shortly and have not put all that
much effort into breeding recently.
I would be interesting to see what people have tried to keep fry alive.
We know of the egg/yoghurt/yeast etc, but what else have people tried?
Peter