I bought 2 peachy/champagne angelfish in January 2020. They were between dime and nickel size, and now their bodies measure about 2" across. I've had them in a 30 gal
aquarium with 3 cory cats and 6 tetras. I have been a less than a wonderful fish keeper the past several months because my 87 year old Mom is taking a lot of time, and I'm trying to get my 63 year old special needs brother out of an abusive marriage. As my grandmother used to say, I'm about one step ahead of a running fit!
I check water parameters, do water changes and vacuum gravel regularly (every 7 to 10 days). That's all been nitrate/nitrite/ammonia 0/0/0, pH ~7.4-7.5, but my tap water is a little higher.
About a month ago I noticed one of the angels had what looked like ich, only black. He also had a handful of places on his side where the scales seemed roughed up. There are no black specks in the ruffled up scales. I think there are two things going on. I got online and learned that black ich is a thing. Meanwhile, the other angel was symptom-free.
I treated with ich-X. I also noticed there were some opaque spots on the pectoral fins. At this point 2 of my cory cats died. Then I noticed that one of the ventral fins had turned dark where it is very thin & flowy. I thought it might be fin rot and treated with doxycycline. The darkened part disappeared (fell off?). The other angel was still symptom free.
The black ich was still there and the roughed up scales were, too. I read that Cupramine could be used for black ich, so I have started treating with that. Today I noticed the anal fin on the other angelfish has some darkening of the ribs in the fin. I have read that erythromycin can be used for treating fin rot, but the Cupramine has to be left in for several more days.
1) do you think I am on the right track with diagnosos and treatment, 2) if so, can I use erythromycin with the Cupramine?
I welcome any advice and just want my angels healthy and happy.