Fuzzy white poop

[MonsterFishCreeper]

So I posted this in another sub forum but it was thread jacked horribly. My GT I picked up last week is having fuzzy white poop. He hasn't eaten since I got him and appears to be stressed. All uneaten food has been promptly removed from his tank. 0 ammonia, 0 nitrite, 10ppm nitrate, 7.4 ph, 73 degree temp. Any help is greatly appreciated he is a 6.5" beautiful male GT and I paid a decent amount of cash for him so I really want him to pull through whatever is going on. Here is a picture of the fuzzy white stuff in my pre filter.

 

[MonsterFishCreeper]

Really hoping for some help on this one. His poop is definitely white and stringy. I think the fuzziness of it on the pre filter was just it breaking down because it had no where to go. I took those off and it does go into the filter now. I have been dosing with ParaGuard for three days because he had a hole in his tail and I was concerned with tail rot. He was also "flashing" or rubbing himself on things so I went that route and the rubbing has stopped. What is this poop about? He refuses pellets but did chow down on a few tetras over the last few days that I mistakenly thought would be too fast for him. More stringy poop though and it looks a bit swollen near his anus.

 

[MonsterFishCreeper]

Bump. Any ideas on treating this?

 

[Iron Cat]

Fish Bendazole worked for me when mine had white stringy feces (internal parasites).