Just keep an eye on him with the tetras, beautiful fish! People have reported both luck, and minor aggression between badis and tetras, but a close eye will tell.
Like others before me have stated, that is a scarlet badis (dario dario). It is a beautiful male specimen. They are pretty aggressive for their size but can be kept with other fish as long as you keep an eye on everyone for a bit. I kept them for a bit and loved these little nano fish.