That's the funny thing about the sh's. They touch it, it doesn't hang on to them, & they just mosey away at their leisure. By accident & ignorance, not out of unconcern for their welfare, I came to learn through exp. that seahorses are not as sensitive to nematocysts as commonly believed. I've had cb seahorses for 4 yrs. The 1st tank I put them in was full of many types of corals most people would suggest to avoid w/ sh's. I had many types of euphyllia, bubbles, open brains, an alveopora, ricordea florida, various other softies and a RBTA. About a year after I added the Sh's I was told that basically everything I had placed them w/ will sting them. They were very comfortable, healthy, and active in this tank - they came up to beg for food almost as bad as a puffer would whenever anyone was looking. They hitched on & rested against my corals w/out any sign of distress.
I'm not suggesting it's a good general idea to keep SH's w/all anemones. As Dr. Shimek has written many times, their sting is very strong when in contact with their targeted prey items. My RBTA has always eaten squid. Before I put my Sh's w/it, I tried many types of food including silversides & sm. fish carcasses (I used to work at a LFS; these weren't in very short supply). It really only reacted strongly to squid. I think I'm lucky that I didn't put the SH's in w/a RBTA whose prey item is fish; were this the case I'd probably have lost them long ago.
I think as long as your SH is healthy & robust, as cb ones tend to be, I think its bony armor plating is very good at protecting it from nematocysts. I know a few others on this site who are keeping them successfully w/stinging corals most on the sh forum would strongly recommend against. I always watch very closely when I introduce an inhabitant to the tank to see how the sh's react to it. They are very curious & brave; usually the 1st to check out a new addition. I don't take my eyes off the tank until I have seen physical contact w/the sh's because I want to make sure it causes no distress. So far, I have not had a problem. I would think in 4 yrs, I would see one. If anything, fish w/their movements, have been more of a stressor. Sorry for the length of this post...:eek1: