Greech, the RBTAs and flowers seem to present no issue as long as there isn't physical contact. They have been together going on two years now. On the other hand, one of the flowers was getting brushed on one side by an RBTA and the flower's tentacles are retracted there. I put a piece of liverock between them so they could no longer touch, but now, several weeks later, the flower's tentacles still are a little retracted on that side. On the other hand, the RBTA was back to normal in no time. So Sugar Magnolia, from what I've observed, there isn't chemical warfare between the species so much as just contact warfare, if you will.
Thanks Minh, I've had that mag for nine years now. It was under PCs for a few years, then MH and now T-5s.