Just as a data point, here's my experience so far:
I picked up 2 Dario Dario from LFS 2 weeks ago, one bright red, one pale pink, for my Mini-M at work
. I also picked up some frozen bloodworms and fed those each morning. I ordered fairy shrimp and walter worms to culture for live food.
The red fish lasted 2 days and then disappeared. Although the tank is moderately planted, I looked hard enough that I should have found him if he was still in there. I think the CRS ate the corpse. The pink fish didn't die, so I have to assume he was eating the worms, but I never saw it.
Today my walter worm culture was finally ready so I fed those and he loved them. I got the worms from "livefishfood" on evilbay and they were very easy to start and feed, if a little smelly (mostly yeast smell, though). I'm hoping it's easy to reproduce also since so far it's the only food I've seen the little bugger eat...
The fairy shrimp (from "eeandss" are still too small to be practical, but I have ~100 hatched and growing.