Clownfish: parasite or poop?

[TEX]

So I’ve had this juvenile clown (1-1.5”) for one week. Only fish that’s ever been in the tank. Came from a qt setup, but I did not personally qt him. For the first week he ate almost exclusively mysis.

Today I noted he had this very long white string coming out his rear. I’ve heard this can come from eating heavy mysis, but what’s the likelihood it’s a parasite?

 

[Big G]

Stringy white poop gets our attention. But we also look to see if the fish eating like crazy yet its stomach is pinched in.

 

[TEX]

No stomach pinch, and eating a lot. Doesn’t act lethargic

 

[Chrisfish]

What are you feeding him?

 

[Big G]

No stomach pinch, and eating a lot. Doesn’t act lethargic

I'd consider slightly altering the food and then observe.

 

[TEX]

What are you feeding him?

Was feeding frozen mysis for about a week, switched over to LRS reef frenzy today. This showed up today for the first time