This "smell" is the reason that I'm designing a new fish room on my new house which will compliment a new inwall tank. I'm used to it; but my family complains (especially when company is coming over).

"Honey, I can make it so that you don't smell a thing; but I have to upgrade the size of the tank and build a dedicated fish room" was how the conversation went. Done deal.

The only thing I "smell" now is a new tank build thread. Hee Hee!

It could be humidity. Try opening a few windows, running a fan or getting a dehumidifier.

A properly running reef system shouldn't produce any smell detectable in the room it's in unless your nose is right on top of it.