I have a 55 gallon well-established mildly-brackish tank (1.010-1.015 SG
). I did a 20% partial water replacement 3 days ago. Today my balloon molly is showing red patches between her pectoral and tail fin in the same spot on both sides. She is showing no other symptoms, nor are any other fish. She had 7 fry on July 24. All tests show my levels are fine. Tank has 78F temp. Anyone have any ideas? I know of hemorrhagic septicemia, but my ammonia levels are fine. What else could it be? These patches are EXACTLY the same on both sides, and nowhere else. I don't know how to describe them, except that they look like abrasions or bright red burst blood vessels under the scales (I know, I know... hemorraghing) but the symmetry and lack of symptoms in my other mollies and fish? And I JUST did a partial and am OCD about my water levels.
Thanks in advance.