Hey guys so this is Shiro my older betta fish, as you see he has rotten fin. For this I am using 100 mg of kanaplex per 2.5 gallons, and rising the dose every 48 hours. Right now he is at 300 mg. The thing is that I don't know what are those red areas. I believe is for nitrates but his fish tank is perfect: GH:4,KH:4,pH:7.0 and Nitrates, they always, technically are at almost 50 when I am going to do water change, so it's nitrates are around 10 after the water change and for almost the whole week. If this red spot aren't for nitrates pls could you tell what is it? Thanks in advance. Also, could you tell me if is there is a better way to cure him?