

What is this on my parents betta?
This is my parents betta that I am currently making a bigger and better tank for. I noticed this grayish patch on his side that kind of protrudes out. Is this some sort of fungal infection, and what can I do to treat it? I know he doesn’t look the best, but I was hoping putting him in an actual and better tank would fix most of the problems itself. I tested the water he’s in and it said 0 ammonia and nitrites but around 20 ppm nitrates. I’m worried this is a problem that a better tank with better water quality wouldn’t be able to fix on its own.
Thanks