ok, sounds good so far.i think he may just be stressed,but it is possible that some type of illness may be just showing it's first vivible signs.Keep him in his new space and see if things change.
I also had that problem as well,when i first got mine.I was going to move both of my gouramis to a 10g,because i was affraid my tetras were too wild.But eneded up only moving one,on farther inspection, i noticed that one gourami was not adjusting as well as the other.One was holding his own in the tetra tank and the other stayed hidden he was also being bullied by the more dominate gourami.So, i only moved the wimpy one,lol.Now, he is fine and dandy in his new tank, no stress, no stringy poop.Although,we are now dealing with hole in the head.This paticular one doesnt really seem to have it,but is being treated anyways because he had been in the same tank as the one that does have it.
Anywho, i wish you gl on finding the problem.I am hoping that it is just as simple as a case of stress.