Hello Chen,
.. it´s a ptretty good shot of the poop, you can see an partially empty tube, I´ve tried on other fish (colisa) to examin it (more than a year ago), also with a microscope, did not find anything. Also I´m not that skillful to determine parasites. Most of them I looked at pictures in the net that gives basic ideas what to look for. As I said, I´m not that skilled, but it doas not appear to me as a parasite - however with a little decomposition involved, it could be anything. And the picture is good but can not show details ,a skilled person needs to compare with typical signs of parasites (any hooks, certain shape, head-shape,...).
I learned that white poop is indicating some intestine problems. Colisa had a swollen stomach and increased organs. After treatment with jbl-furanol the poop got better, but the fish was lost anyway.
I use the Mikroscope of my kids (inexpensive), it is good enough to show a lot of detail, even putting the cheap camera on top makes pictures that can be shared.
Poop of my clowns is very compact and heavy. I rarely see them doing it, only guess some findings are from Cat or Clowns...
It would bne helpful finding out who is the owner of "it"
Sorry no real advice, I know.
I still love that large clown you have...
Wolfram