this seems a little strange...should I be concerned? This isn't the first time this little tadpole has done this, I've only been able to capture it this morning after seeing it 2-3x/day over the past 2 days.
Sometimes I've seen him swim upside down for "no reason" and other times it has been after eating or resting. You see it at the end of the video clip, sorry it's so long!
Gray Tree Frog Tadpole - YouTube