Was Sauron a Balrog?

[Aganzir]

Originally Posted by Legate of Amon Lanc

But if fire-spirit is a fire-spirit... anyway, it looks that we can't tell even what Arien was... if she was Vána's, well, then what was there about the fire? The flame of youth?

I'm not sure if you're saying that we don't know if Arien was a fire-spirit or whose maia she was... At least I think it was said quite clearly that she was a fire-spirit (see the quote Nerwen provided).
But as for her connection with Vána... Did there need to be more reasons than that the flowers in Vána's gardens enjoyed being watered with the dew of Laurelin?

Originally Posted by alatar

Maybe he had one or two dancing around within his forge - no need to cut trees then.

One or two Arien-like naked flames dancing there would surely have been more disturbing to Yavanna than some occasional tree-cutting.

Originally Posted by alatar

Melkor and Manwe were brothers but went separate ways. Why can't fire spirits do the same?

Were the fire-spirits alike in every way (ie. did Eru "create" them to be some special kind of spirits), or was the only thing they had in common that fire attracted them?