Dipping is a proactive measure that should be taken by all to prevent unwanted predators from entering your tank. There are a few trade offs, a freshwater dip will kill just about everything, even bristle worms and snails. If you're not dipping, you are simply playing Russian Roulette with your tank. If you have a 10 gallon nano with 2 or 3 colonies of Zoanthids, dipping isn't that big of a deal. However, if you have a 70 gallon tank with $ 2,000 invested in zoanthids, dipping is a life saver. Dipping alone simply isn't enough. Close inspection is just as important. After a dip, close inspection under actinic lighting will highlight Nudibranch eggs that are just as deadly. The dip won't affect them, so you must manually remove them.
Sea Spiders, Sundial snails and non reef safe inverts must be kept in check, or devastation will surely follow.
Geoxman, I had the dip removed to make room for new stickies. You can find them under the zoanthid info draft at the top of this page. There are so many dips out them, just try them and use the one that you like. For non medicated predator prevention, I would strongly recommend a freshwater dip of some kind.
Mucho