carpet anemone
 

is it true that S. haddoni will eat anything that got stuck onto it? any experience?

They're pretty darn sticky. If you touch the tentacles you'll likely pull the tips of the tentacles off the anemone as you pull your hand away. So if something gets stuck, it's probably toast unless it's strong enough to pull away quickly enough to avoid getting stung too badly.

They will eat any smaller fish that comes into contact with them. I have lost a few gobies to mine. I have a bicolor dottyback menace that has figured out it can chase fish into the carpet and.............they are toast and quickly. The only thing I have managed to save that fell into it was a sea hare but I was really quick. The hare did shoot out lots of black ink though.