I would definitely try returning to an LFS, or look up a local aquarium club.
While it is not a sure bet it will die, odds are against it. Most will die in 12-18 months as stated in another thread. The arms simply start to fall off and most people assume it is being attacked until suddenly it just is no more.
It will not "harm" the tank, except the microfauna that it eats which are desirable. But otherwise it will not hurt anything, no.