The reply is a little off topic to the original topic, but
I'm not aware of any invert, snail or crab that a trigger won't eventually go after. It's just nature at work. If you go to the homepage here to the left and click on information for hobbyists, there is a thorough and detailed description of pretty much any fish or invert.
As far as my cleanup crew, I've pretty much lost track of what all is in there. I know I have red, blue and left-handed hermits along with emerald crabs. Cerith, nerite, astria, mexican turbos, cortez and bumblebee snails. Probably a few other types too. It was too tough to pick up what I needed from the LFS, so I ended up buying a cleanup crew online. They asked what I had, what I was trying to accomplish, and where the current problem appeared to be and pretty much filled it in for me. In 48 hours the tank looked sterilized, so it must have worked. Most snails and crabs have a strong point in what they do, and that is the best way to decide on what you need.
I received an order form SWF.com yesterday and was very happy with it.