It's not just his size, it's his waste production. He will have that thing pooped up in no time, even if he is the size of your pinky (Which is about max size for him being in 8g.) and for all I know, you are 10 feet tall with basketball fingers.
And if your boyfriend has a quite large one in his massive aquarium, I doubt it's a bristlenose. (I'm not sure what your definition of massive is either)
If you want tetras, only look into the tiny ones smaller than neons, such as embers.
Like others have said, most killifish would be ok.
Ideal would be a betta.
Maybe a few pencilfish.
or go to your LFS
and see what they have swimming in there shrimp tank.
I have a scarlet badis badis. Looks like a Dwarf Gourami but more intense colours. About as big as my fingernail.
There are other tiny tiny fish, that are (at least at my LFS
) kept with the snails and shimp.
You are very very limited with 8g