I currently have 4 nassarius snails in my tank. They are good at moving sand around but become stagnent if the tank is not fed (every once in a while). However, if you have fish that you feed regularly they will come out and greet you at every feeding!

Jim, wouldn't a fighting conch be a bit large for the 12 gallon tank? From my expereinces conches tend to redecorate the tank (re: move stuff around by bumping into stuff) since they are so large. I have to admitt that I have never owned a this particular conch. On a different note it was interesting reading Wet Web Media RE: sand sifting stars. I did not realize that they deplete the sand's fauna so easily, it was a good read.

Christopher