2 Q's: Agrro Danio and Lights

I've got a 10 gallon tank with 4 rasboras, 2 cory cats, and 1 danio.
The danio chases the rasboras constantly and I think has been
attacking one of the corys, as its fins are kind of shredded. I would
like to lower the stress level of the fish by calming down or removing
the danio. I'm thinking:

1. Get a couple more danios and let them chase each other.
2. Remove the danio. But what to do with it? I don't want to kill it,
will an
LFS take it back?

And as far as lights go, do fish need an aquarium light? I bought one
of the full spectrum lights but the tank seems really bright and it
seems to bother the corys. They've got a shell to hide under but it's
not much darker there.

Thanks in advance for your time, above email does not work, plase
reply on-group.