Hello everyone, I’m new here. I’ve had an aquarium for a few years. I have a 6 month old angel fish who is very sick and it happened rapidly! Wednesday she was fine. Yesterday I noticed a small growth on her left side. Today it’s so much worse and she is swimming very erratically. Seems like she is on the verge of dying. I’m so upset. I don’t think she can be saved, but maybe someone can tell me what happened so I know what to avoid next time? I’m attaching a picture. Thank you.