they will be fine in the tank...if not this guy is going to have a few problems! lol
http://www.aquariacentral.com/forums/showthread.php?t=184291
just missed your post. i'll research these poly bands and see what's in them.I think rubber bands have oils and lubricants in them, so I would steer clear of using them in the tanks.
Can you imagine if one of them snaps and gives your Oto a whiplash?