I got three Danios with my betta in the 10 gallon tank. When should I start feeding them and how many flakes for three?

I've got three little Danios too. I just feed them until they aren't hungry anymore. They're top-feeders, and they do have a hunger limit. Of course, yuo might want to let someone else more experienced than I to answer your question.

in my comunity tank (listed in sig) they get pinch of flakes in morning and eiter bloodworm, pellets etc "pinch" in evening.

i do the same as loz..... just a pinch will do.