Lump on cardinal tetra?

[ella777]

One of my cardinal tetras has a small yellowish lump on the side of it.
His colour is great and hes swimming around normally with the others.
It doesnt look like ich, maybe a tumour?
None of the other fish have it.
Hes about 4 years old and 1.5 inches.
I cant seem to take a picture of him unfortunately

 

[Colin_T]

video if you can't get a picture
upload video to YouTube, then copy & paste the link here.
if you use a mobile phone to film the fish, hold the phone horizontally (landscape mode) so the footage fills the entire screen and doesn't have black bars on either end.