In the meantime, I was wondering if this is a common thing for these fish to develop and if I should be worried or if there's anything I can do for him. He's acting normally and eating fine. He's just a tad gruesome.
Thanks!
Update to include tank conditions:
Nitrates and nitrites ~0ppm, alk ~80ppm, hardness~120ppm, pH~7.2, ammonia~0-0.2. These values may be off because I'm using a cheap test strip indicator, but the values have been constant for a few years so I'm assuming they're OK.
Tank is approximately 165 gallons with a vinyl liner made for ponds. He's been in it for about 4 months. I don't think he's eating it. He lives with another pleco (same type, age, and size, ~16"), a few goldfish, and a few other mismatched fish. None are aggressive and most have cohabitated for years. The most recent additions were added about 3 months ago: two goldfish. They are healthy.
Temperature is variable and ranges from 78-83, depending on the weather. It is heated but gets a little toasty in the summer. Light is from east and south facing windows. Substrate is gravel. There are a few larger rocks and a terra cotta pot (I don't think the plecos eat the pot either but it's only been in the tank for a few months.).
These may not be ideal pleco conditions, but it's the best I can manage for my guys. However, any suggestions on making things better for them will certainly be appreciated!
Another edit: I'm going to attempt to insert a picture. I apologize for the quality (especially the reflections!) and size. I tried to reduce the size and resolution as much as possible while still allowing the problem to be visible, but I'm not very good at this!
