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glass anemone is another name for aipitasia right? then a bergia nudibranch is the way to go.
Personally I'd just take the LR out and squirt a bit o lemon juice that you can get from any supermarket. I know the book says to "inject" the stem of the anemone but I didn't bother - mine was a little one and the droplet of juice caused it to turn white and shrivel. Never to be seen again.
In addition to what Phil said, You can also mix up some Kalk paste in a cup and let that sit for an hour. Turn off all the pumps in your tank, then take a syringe and suck up the paste part from the bottom of the cup and squirt a little on each aiptasia. It usually melts them right away (as long as they don't retract before you squirt them). Then you wait about 1/2 hour and turn your flow back on. The little bit of Kalk in the tank will blow off the rocks in time. Just be cautious not to squirt any on your corals.
I agree with both Phil and Brian with certain caveats.
Berghia Nudibranch is great but their diet is highly specialized. They only eat aiptasia, meaning they will die after all aiptasia are consumed. If you must take this route, try to get it from someone who has one and pass it on to another hobbyist after the job is complete.
Kalk is a great solution. Just be careful handling it as it is caustic (ph approx 12.4). Washing soda (Sodium Carbonate) will work as well (caustic ph about 11). You can make it by putting baking soda (sodium bicarbonate) in oven for an hour at 300 degrees.
Vinegar and lemon juice also work well.
Peppermint shrimps might work. It took mine a month before it found the last aiptasia in my tank.
Some butterflies will eat it, most notably the Copperband. It is fairly reef safe, with exceptions of featherdusters, koko worms, etc. and may nip clams. Notorious hunger striker though.
Of the commercial products, Aiptasia-X probably works the best.