Hi... I've had a betta that lives with a couple mollies in a 29 gallon tank, when I first got her early this year, she had a tiny bump beside her dorsal fin where it looked like her flesh had exploded and the skin grew over it... however, the bump has grown more significant as she grew and now it's almost 1/5 the size of her body, without the tail. It looks pretty rough and the shape isn't like a perfect spherical bump, it's completely not geometrical like a small mountain grew on my betta back. My betta has dark green scales and crimson fins, but the patch on the back is black and some white on it. It doesn't seem to be affecting her, but I'm getting a little bit more concerned since the spot is getting bigger.