Also, maybe he is just stressed from being in the 10g...why did you move him, because he chomped your BTA? Or because he was acting ill?
How long have you had him? If you have had him a while and there are no signs of illness, I would remove the BTA, maybe take it back to the LFS
for trade in and give him his space back... BTW Love their personality... I have an empty 50g, was thinking of getting one... but not sure about my space or their care levels as of yet.