BTA's do have a limit to the light they can handle. They should be acclimated to new lights. The good news is that they are very mobile and will move to a spot they like - generally at the right light level, place to hide foot in rock hole/indention, with current flow at full extention, but mild current when the retract towards their base.
BTW - if you have powerheads, the best bet is to leave them off until the BTA settles in their spot. They have a knack for finding the blender.