Sounds like your tank is cycled! You want some nitrates remember. No need to change the water every day. I forgot how big your tank is, so if it's under 5 gallons, change 50% of the water twice a week. If it's bigger, once a week.
You can try using some stress coat, but clean water will heal his fins too. Are you noticing any clear on them? If you see that, that is the new growth.
You should switch to pellets, and soak them for about 5 minutes before you feed them to him. If he won't take them, try soaking them in some non-oily garlic juice.