Thanks for all the replies.
Someone wrote that my tank had been set up at Aquarium Showcase. That is where I bought the tank and I am proud to sponsor them on my radio show. The tank was not set up there though, but they set it up for me at my office- just to be clear. Aquairum Showcase does a great job of both servicing my tank and setting it up throughout the process of adding things. I am a little embarrased to call them and say "Hey, can you come down here, something has gone rancid in my office." They already think that I am crazy - I visit there all the time and stay for hours.
Anyway, I sniffed all around the tank and had other people sniff all around the tank. Some people said that it smells fishy while others now agree that it may be a dead animal in our crawl space or attic of the office.
All my snails are doing great, everyone in the tank is doing great, so I am going to chalk it up to a dead animal. I put some charcoal deodorizer that you would put in your closet in my office and the smell is definitely less.
I think the problem here is that this tank is on my desk and I have become obsesed with the tank. Most of the visitors to my office wonder if I am working or just in a daze staring at the tank. Anyway, I guess that the obsession will wear off soon enough.
If you are in the area of downtown Alpharetta, stop by and see me and sniff around for me. Duffy Realty, 10 Cumming Street (on the corner of Main and Cumming) Alpharetta
Again, thanks for all the replies - you guys are great!