OK, this might be tome, and if it sounds like I’m talking AT you, I’m just, just using you as an example. No this won’t help your angelfish, but your long-term experience in the hobby is what I’m concerned with at the moment.
A few things you can do going forward to vastly improve your experience. First...quarantine your fish...ALWAYS. This is among the most basic things one must do to keep a healthy display. Listening to the "I've never quarantined my fish, and have never had a problem" crowd is like listening to someone poo poo seatbelts because they've never been killed in a car accident from not wearing one. Never mind that they've never been in an accident. I'm sure I don't need to point out the fallacy of this logic, and the same applies to the false logic applied by the no quarantine crowd. Quarantine is one of the easiest; most sure-fire ways to keep pathogens out of your tank, and protect yourself from frustration, stress and financial loss. Not to mention that it’s not really fair to the fish to introduce a disease-ridden roommate into their space!
I’ve heard every reason imaginable as to why someone doesn’t quarantine (usually in the midst of a “Help, my fish have Ich!!” post. They are all BS…period. Simply dropping a new acquisition into a tank hoping the worst doesn’t happen is rolling the dice, and sooner or later you’ll lose. Running the search function on any reef BB for the word “ich” will bear this out. If you don’t have room or the funds for a quarantine tank, you lack the ability to engage in the hobby.
A small, 7 gallon or so tank will do the trick in most cases, so lack of space or funds is no excuse. Every reference on fish keeping spends a fair amount of time explaining the importance of the procedure. So, either the keeper doesn’t do his due diligence, or reads the information and for whatever reason, decides to ignore it.
Second, research your fish thoroughly and select hardy, trouble free species. This subject is apropos to an article I’m finishing up about transitioning from freshwater to marine aquaria. There’s no reason that it has to be any more difficult than freshwater, and there’s absolutely no reason that you were destined to be dealing with this problem. The problem is that too many beginning hobbyists set themselves up for failure. There are scores of delicate species out there, and then species that you practically have to toss out on your lawn and get your dog to chew on it for a while to kill it! There are plenty of graduations in between too….so why pick a herladi, or Hipp tang, or Regal angel, or Longfin anthias? The reason is that many aquarists pick fish based not on research, but color, emotion and whim, or even bad advice, and neglected the suitability of that particular species for captivity. Simply picking the right species goes a long, VERY LONG way toward initial success in this hobby, and for that matter long-term success as well.
I learned a long time ago to stay away from certain fish, long after my experience level made keeping them more than possible. With a little car in picking the specimen, and a little luck in getting an individual that wasn’t caught with cyanide, I can keep a heraldi, but why bother when the C. argi complex is as tough as nails? You can stock a tank with an Orchid dottyback, a Banghai cardinal fish and Argi angel, toss them in and almost ignore your tank for days at a time. A beginner selecting even a somewhat delicate species makes zero sense.
Moral of the story…Quarantine. Know it, love it, be it.
Research well, pick the hardy fish, at least for now. There are plenty of them to choose from…you’ll have plenty of time to keep the iffy ones later. Your experience in the hobby will be transformed.