Peppermint shrimps... really "reef safe"?

I've just found an old post on that topic and would like to add my
observations.
Lysmata wurdemanni (Peppermint shrimps) do prey upon Stomatella snails. at
night i used to have about 40 of these little algae grazers only on my front
glass (wonder how many 'round the tank), after introducing the peppermints
they slowly started to disappear, some were just mutilated (they often leave
predators eat their hind part of the body as a gecko would do with its tail)
but soon many stomatella shells started to lay on the tank bottom. One night
i've found one peppermint shrimp grabbing a grazing stomatella and being
"attacked" by a second, bigger shrimp, who stole this freshly catched prey.
Stomatellas are almost extinct in that tank and i try to move the few
survivors to safer quarters (my nanoreefs)
Peppermint shrimps also will attack and kill other tankmates (for example
freshly molted crustaceans, also they once killed a still alive Lysmata
Debelius which was trying to get acclimated in my 25Gal.) and will
dramatically decrease populations of microfauna as various 'pods.
I recognize them as a great resource for Aiptasia problems, but i'm not so
sure they can be considered "reef safe", ok they will not eat corals, but
our tank's equilibrium is based on many other factors which the presence of
peppermint shrimps seem to threaten.
Any similiar experiences?