i did find a good explanation of what nems do have....
"The definition of allelopathy:
Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have beneficial (positive allelopathy) or detrimental (negative allelopathy) effects on the target organisms. Allelochemicals are a subset of secondary metabolites, which are not required for metabolism (i.e. growth, development and reproduction) of the allelopathic organism.
Allelopathy is characteristic of certain plants, algae, bacteria, coral, and fungi.
Anemones
might have chemical weapons (I'm not sure that they do!) but they DEFINITELY conduct physical warfare.
They use nematocysts- their microscopic harpoons. They can shed nematocysts into the water column. They can choose NOT to shed nematocysts as well.
Anemones (different spcies) need not actually touch to harm one another and they can certainly sense the presence of another anemone.
That doesn't necessarily mean they will feel threatened enough to release nematocysts en masse.
A good filtration system might keep the number of shed nematocysts down to a minimum.
This might explain why some people can keep different anemone species together and others cannot."
Host anemones allopathic interactions - Reef Central Online Community
notice the "might". i have read and heard many people's opinions, but have not seen any proof of chemical warfare. maybe i have missed something? maybe op was referring to nematocysts, which is different imo then chemical warfare.