Delaney Sue
New member
...lump is what appears to be? My betta fish has a big black lump under and behind his fins, and behind the black lump is what appears to be an air bubble. From inside the air bubble I can see a tiny red vain. He acts fine, eats fine, but this big lump and bubble seems to put him in pain when he lifts his head up for food. What is this and what can I do to help him?