I'm by no means expert on Black Neon Tetras, as I said before
I had four of them long time ago, and I bought them because my LPS
told me they're hardy and will go nicely as the first fishes. I had them in the 60 litres tank with Dwarf Gouramis and few other tetras, and they were very calm and peaceful; all over the tank also, but didn't eat anything from the bottom.
As for Danios - I never had any and have no clue about them whatsoever, I'm afraid.
But I'm pretty sure someone else will help you with that and will correct me if I'm wrong about Neons