Truus

Water parameters are fine: Ammonia is 0.25, Nitrite 0.0, Nitrate somewhere between 5.0 and 10.0, pH 7.2, and water temp is around 80F. I have not done a water change for a month now but the water is crystal clear. I have a planted community tank that I started almost 3 months ago (but the filter, driftwood, rocks and bio-rings had been cycling for 2 months prior to that). The tanks is 55 gallon. I am a newbie and my goal is to do minimal water-changes (taking Cory's advice) This was the biggest and most dominant minnow in the tank. A noticed about a week ago that he became less aggressive, not parading around and chasing other fish. It is just yesterday that I noticed the blotch. About 3 weeks ago an angelfish died (it might have been fin-rot but he (most likely) was also harassed by the dominant angelfish) and a few days later another one was floating. I then immediately did a 5 day course of antibiotics (erythromycin) and the angelfish bounced back right away. She is doing fine now. I have 3 angelfish and about 25 other fish from neon tetra's (smallest) to minnows (largest) and have no other fish die in the last weeks. New in the hobby anxiety Truus

This is the picture that did not upload in my earlier post. Can anyone identify this skin issue?

This is the largest minnow in my community tank. Today I noticed these red blotches just above the tail. The red area is in the flesh and the skin above it looks like it is flaking off, or at least it is loose. None of my other fish have this issue 'yet'. Does anyone have an idea what this is and how to treat it? I removed the fish from the larger tank.