It depends on the fish I think. My bettas either ignore the bubbles or enjoy playing in them. My king
betta, King Koopa spent the better part of the first day in his new tank trying to swim down the bubbles from the top and also sticking just his head into the bubbles. My veil tail Mako will spend about 5 full minutes every few hours just riding up the bubbles and swimming back down.
Do you have any kind of hiding spot in your
QT tank? Your fish just might want to relax a bit and feels more secure relaxing in his/her strange new place being hidden. If there's not a hiding spot for him/her you might want to add a decoration, plant, or terracotta pot for him/her so s/he can relax a bit and feel more secure.