Yes, and no. Anemones aren't aggressive in the same sense as an aggresive fish might be. Most fish/inverts recognize the hazard of hanging out in an anemone, and will simply avoid one. The threat to corals/stationary inverts is much greater. Anemones are mobile, and if something is occupying their chosen spot, they will knock it over, and sting it in the process. Anything they pass by while moving is likely to get stung. Their tentacle tend to float around, and can snag other stationary objects. Careless fish can get stung, but this usually isn't fatal. A sick fish might be eaten, but usually a large healthy fish can get away.
We have a curly-q anemone in with our trigger, lionfish, eel, and burr fish. The burr fish gets stung frequently--he's kind of oblivious to everything--think of a big dumb puppy. He's also gotten tagged by the lion fish (he actually was swimming above the lionfish and basically speared himself--the lionfish was not impressed and shook him off. The lion fish now will move out of the way of the burr fish). He has white patches for a while, and they heal up within a day or two. He has learned to avoid hitting the tentacles with his eyes.
I'd avoid anemones until your tank is well established. It's been my experience that the 'nice' ones--carpets, LTA, etc--are sensitive, while the junk ones--aiptasia, curly-q's--are resilient and almost impossible to kill. Clowns won't host in them, however, and they are nasty to tankmates.
!). I find my carpet more annoying because once they stick to you they won't let go. One must shake them off their skin. As for the tube question it might be a Tube Anemone which is highly predatory. They will eat all fish that come near them. Either that or it may be a Long Tentacle Anemone that has sunk its base into the sand (they do that pretty frequently.