How did you get your bta off the rock? I`ve got 2 large ones to try and pry off their spot.

I use the tickle the foot and patience method.
I ensure the BTA is on a rock I can remove
Then I fill a small container with tank water and put the BTA and rock in it. I lift the rock so that the BTA is hanging off the rock and tickle its footing it can take upto and beyond and hour.

J

removing BTA's
 

In Albert J. Theil's reference "Heteractis Type Anemones" he advacates the use of ice cubes. (I guess you could put one in a ziploc) .It supposed to be especially good if they are on the glass. Just cool the edge of the foot a little and he says it will release.
Might work with BTA too. With care it seems to me it could be a low stress way to remove and move them.
What do ya think?