Danios are always cool. If you have big groups of them they won't be aggressive. I have 7 Zebra Danios and they really aren't aggressive. But they move around alot...so maybe not so peaceful. But they're quite pretty.
Dude thats epic!Tetras(glowlights especaly under the right lighting) are cool, slower moving schooling fish, danios are cool also but they are very fast and dont school as much.
In my first tank, that was a 29g, i had zebra danios, kuhli loaches, and a opline gourami. I loved it.
Check out my avatar thats mom the opline gourami, it actualy says mom on the side if you look carfully