Ha! I forgot part of the common name for these - it isn't "fire anemone" it is "Hell's Fire Anemone"!
50+ years ago, when I was a kid, working in a pet store, my boss ordered one. We put it in our big anemone/clownfish tank. It filled up one whole side of the tank. A customer came in to buy a damselfish. I went in with two nets and started chasing after a damsel. Fish were rushing back and forth and some brushed into the anemone. Those looked like they had been shocked with electricity. Some of the anemone's nematocysts got on the net and the damsel I caught in it also died. I was thinking, what's going on here, all the fish are dying for no reason. Then, I figured out it was the anemone....through it all, I never got stung myself though.
Jay