I have no idea if this is relevant, but I'll share.
When I first started fishkeeping, my newly-setup tank (which was in my living room) smelled like the dickens. It was a *strong* musty smell; it would almost choke you. Very unpleasant. I didn't even have fish in it yet - just water and substrate (standard aquarium gravel from my local PetSmart). I eventually figured out it was the substrate, which was odd as I had washed the heck out of it before putting it in the tank.
Anyway, I ran an aerator and the power filter (with carbon) in it, doing large water changes each day. After the third day it got quite tolerable, and after a couple weeks it went away entirely. Months later, after having forgotten all about it, I setup a 10-gallon for a friend of mine and used some of my left over substrate. Substrate + water = same smell as before. Ugh. It, too, went away after running a filter for a few days and changing most of the water a few times.
I can't recall the name of the gravel I used, but I can tell you this: I will not be using it again.
pendragon!