Internal parasites?

[Bobblehead27]

I'm seeing white poo hanging from my fish so I added metroplex into the tank about two days . (It's older so it may be expired. Can't read the expiration date) i just wanted to make sure that I correctly diagnosed this before I go through the full treatment

Hisstomach seems sunk in as if I'm not feeding him. Which is obviously not the case

This is happening just a couple days after my pike died in this forum.
/forum/threads/disease-or-abrasion

 

[gerald]

White poo could be a symptom from many different causes, including intestinal worms and/or protozoa. Unfortunately no, you can't be sure of a correct diagnosis and treatment just based on that observation. Treating sick aquarium fish is mostly guesswork unless you have equipment and knowledge to really sample and identify the pathogens. Even then, treatment is iffy. But metronidazole may be a pretty good guess!