Platy has weird growth
We have an old male platy. Most of our platies are now second and third generation. He is one of two survivors from our original stock, and he wasn’t young when we got him, so he is probably about 4 years old despite his small size.
He’s small but is the father of most of the younger fish, most of whom are far bigger than he is.
For about the last year he’s looked a little worse for wear, it seems like a large part of his tail fin is missing, but he eats and plays like normal. However, I noticed a couple weeks ago that he’s got this weird rough growth or tumor-like thing on his back. None of the other fish have it, and he seems perfectly happy, but I’m not sure what it is.
It’s hard to get a decent picture of a moving fish, but he’s near the center of the photo. The growth is behind his head in front of his dorsal fin.