hi, a friend recently gave me this betta as he was moving away. the betta came to me with fin rot and fungus. i have been dosing him with maracyn for several days and it is clearing up. he seems healthier and more active than he was when i got him. however today i noticed this large thick strand coming out of him. it is slightly brownish in color and bunches up at the end. it has stayed the same length for at least three hours. the fish is sluggish and not hungry. my guess is constipation, but i don't know for sure as i have never seen this before. what is this and what can i do about it?