I haven't tried it with removing tube anemones but here is a suggestion. First clear all surrounding substrate around the tube (dont remove anything attached to the tube), take a large turkey baster, positioning the opening of the baster about an inch away or so from the stuck area, then sweeze the bulb end of the baster multiple times until the tube anenome is free from the glass. It can be a real fore arm workout but it does work for removing anemones off glass or rockwork without damaging them.
Mike