It showed up 5 days in copper. Done with treatment and is in an observation tank. Day 4. I see it getting a bit smaller but still visible.It could be Lymph, but not 100% definitive. Can you post better photos? AFAIK, Lymph comes out when stressed, so it would be odd for it to not display right away, which is the most stressful time, and then come out later. My Angel had lymph as soon as I added her. It slowly receded over the first 2-3 weeks in the DT (no QT for me), and it hasn't shown up again after 9 months or so on her or any other fish in my DT.