[knboak]

Hello, brand new to aquariums in general, and one of my fish recently started having this weird string-looking thing hanging from just behind its gill.

I have no idea what it is, and whether it's something that could contaminate the entire tank.

Does anyone know what this is?

Thanks in advance

 

[MarineLifeLover]

I have honestly never seen something like that, though I find that it helps to search the web for multiple sources. However, it looks somewhat like fish poop which can form long 'strings' when a fish is constipated (not an expert though it could very likely be something else).

 

[Jkkk]

Maybe "anchor worms" parasites?
Check this Link and swipe to anchor worms. It looks to me that is it...

Identifying Diseases and Deficiency Symptoms Before It’s Too Late

Is one of your aquarium dwellers acting oddly or looking different? This could be a first sign of disease.

www.jbl.de