Originally Posted by Grundylady
I was advised to give him some frozen blood worms once a week. And ever since he has been getting better nutrition I have been seeing lots of regrowth.
This is a good point to remember. In addition to keeping the water clean, good nutrition, especially a good quality protein and high protein diet, is very important in your fish overcoming fin rot issues. Not just in fish, but cells and body tissues require protein for repair and growth. So don't just focus on water quality, have a look at what you're feeding and the quality of ingredients. Improvement won't happen very quickly or well with a poor diet.
Gerty, here's my experience with my betta, Leroy, shown in 2 photos:
Back in my care April 11:
And about 3 1/2 weeks later: