I think this has been coming on for a while. I have seen the stings before but didn't know what it was. It is some sort of internal parasite I believe.
I bought a few Dwarf G's about 6 or 7 weeks ago before I read a lot of bad things about their quality these days. Found one to have lumps on it's body right from the shop. Took it back but kept the other 2. Those 2 are actually from different shops. One of those started getting those lumps a couple weeks ago. (The one from the same shop that had the lumpy I immediately returned)
Long story short, neither have been eating right the past few days, hiding a lot and today, I started watching closely after seeing that long stringy stuff in the tank. Both have that excreting from their anus. It just gets longer and will finally catch on something and breaks it off their butt. I would bet that pic is a 12" piece caught on the wood and bent in half. Both of them having this even though they are from different shops is not surprising because they constantly displayed, rubbed and nipped at each other.
I have no place to put them since my quarantine tank is full of newcomers so they will likely not make it much longer.
I just did about a 75% water change. By chance, I did an 80% change 4 days ago. Will likely do at least 50% changes every couple days this week.
There are a few of these symptoms that could be a match...
Paracide-D keeps showing as a good med in all the possible matches. I'm sure that is there med so I will need to find a common substitute if I do treat for parasites.
I guess I will call my LFS tomorrow for some suggestions. No other fish in my tank show symptoms but if this a some sort of parasite, I have no idea how long it might take for others to show symptoms and I don't know if I should treat the whole tank now just in case?
I'm open to suggestions.
Edit: I'm thinking tape worms or intestinal flagellates but I really have no idea. Finding something safe for plants and shrimp my be the kicker.
BTW... my water tests fine. I'm still fanatical about water test and do them quite regularly. Yesterday being the last time and like I said, this fish problem has been coming on for some time. I just didn't recognize the signs.