Well...it dpends on the danio species you're looking at but, in general I wouldn'r recommend them for a biorb either..especially the zebras.
There are lots of really, really nice fish you can keep in there; here's a few; ember tetra, chilli rasbora, dwarf emerald rasbora, celestial pearl danio, otocinclus, betta, green or normal neon tetra, but there's a very, very good reason why most experienced fishkeepers don't have biorbs, and you've just discovered it...
You really can't keep cories in a biorb; the substrate (that you need for the filtration) is far too large and rough for their barbels.
That's not entirely true, you could keep cories in a Biorb but you would have to buy enough stones to cover all of the substrate, this may make it harder for you but it is still feasible
Your choice
I, personally, am of the opinion that Corydoras should be kept on a sand substrate only.