waste from their digestive system
What Is The Long White Stringy Thing Hanging From My Fish's Butt?
Poop, egg?
That's fish poop. In time, it'll poop again and that will fall off.
Mine has the exact same thing, at first I thought that it could be worms...but then I thought it could also be waste...sorry for not answering your ? Btw!!
If it is a boy it is his thing...but girl...is having period!!! Ha ha ha :0