Carrie,
Just to clarify, it seems you have 2 different types of mantis rolled in to one. There are clubbers and spearers...the clubbers generally go after snails, crabs, etc...the spearers will do more damage to fish...
Neither is great to have in a main tank though...and they're smart too...from what I understand, it is very rare to get anything other than a clubber hitchhiking in your LR.
-Steve