I don't ahve a torch, but my frogspawn (very similiar) gets unbelievably huge when it wants too. They are said to be somewhat aggressive, but I've never seen any kind of tentacles coming from it and a plate coral is in close proximity.
I have a large green Torch and the sweepers tend to get longer in a stronger current, so I keep it in a moderate current. Euphyilla species have a nasty sting so give it plenty of room to expand and grow.
My torch never sweeps, but he does get huge sometimes during the day. I would leave at least 4-5 inches around the coral as they can do some serious damage with their tenticles.
