Moving slowly, I can't tell u when I first noticed this. My tank is barely 2 months old. He was a sm fellow has grow a lot. It may look like its growing because he is getting bigger himself. I used API Furan 2 (for Gill disease) The fishes Gill doesn't look larger than it should be for redder than it should be. But I am no expert just a beginner. The medication did a number on my tank levels and almost killed my brown ghost knife fish . But that is neither here nor there, there is no flukes on it and I even put some parasite drops into the tank just in case. Maybe he was born like this and it was so small I did not notice , But if you have seen this on one of your own fish and it is a disease please let me know. Let me know what you think it is and ask any questions. After the medication my levels were 1.0 ppm for ammonia, 80 Ppm for nitrates, 6.0 for pH : before medication and my levels were .25 ppm nitrates, zero ppm ammonia, 7.0 pH. It's taken me a week but my current levels are .0 nitrates ,.50 ppm ammonia, 6.4 ph . If someone could help let me know how to get my levels right again I'm not worried about the pH because my knife fish like the acidity and my other fish don't mind. I was doing 15% daily water changes to bring my levels to where I've gotten them. I have decided to wait a week before doing another water change to see if the tank can get itself together.