So Ive never seen this...

[ppbg]

It doesn't look like poop but something is definitely coming out of this fish. Any ideas?

 

[CassCats]

@Colin_T

 

[BoomerXIV]

It doesn't look like poop but something is definitely coming out of this fish. Any ideas?

It looks like a fungal infection, quarantine that fish immediately

 

[ppbg]

It looks like a fungal infection, quarantine that fish immediately

Done! Thanks. If its fungal though the whole tank wouldnt already be infected?

 

[Colin_T]

Fungus is in all tanks but only gets into open wounds.

Add 2 heaped tablespoons of salt per 20 litres and keep it there for 2 weeks.
If there's no improvement after a couple of days, then get a fungal treatment.

 

[ppbg]

I can't do the salt treatment in my planted tank so if it is a fungus I'll have to use meds. But honestly now I'm not altogether convinced that it was fungus. As I said, I put the fish in my hospital tank. But when I did this whatever it was hanging off this fish's butt fell off. if it is a fungus i'd think something that big would be a an advanced case and no other fish has any signs. The fish in question has no spots any where else on its body. Might it have been an egg sack maybe? I don't know if they have "egg sacks". Maybe it really was just poop.

But I'm not ruling out fungus. I'll keep an eye out for any odd growths and if something does crop up I'll medicate the tank.

I appreciate everyone's help. Thanks!

 

[PheonixKingZ]

Why can’t you do the salt treatment in a planted tank?

 

[Colin_T]

The cardinal tetra in post #1 has saprolegnia fungus. Just use salt. The dose rate is safe for plants.

This type of fungus can fall off a wound if the wound has healed to some degree.

Chances are it won't come back unless the fish is injured again.

 

[ppbg]

Why can’t you do the salt treatment in a planted tank?

I was always told (and Dr Google appears to agree) that salt hurts plants

 

[mbsqw1d]

For the period of time the salt is in the tank to treat the fish it'll barely have an impact.

 

[PheonixKingZ]

I was always told (and Dr Google appears to agree) that salt hurts plants

That is false. The treatment that @Colin_T suggested is completely safe for both fish and plants.