Betta Fish: Got him on sunday 12/14 and just a few days later he’s looking much better

the first 2 pictures are when i got him on sunday 12/14 and the last picture is from today 12/16

sunday had to run to petsmart for dog food and a snail for another one of my betta tanks, and of course as most do i stopped to look at the bettas they had just because why not. ended up seeing this guy in the cup, he was kinda floating on his side almost looked like he was ready to pass on and i just couldn’t pass up on him. his tank is a little bare at the moment because i am treating him for a few spots of fin rot and wanted to get him at least in a better environment. his 10 gal currently only has drift wood placed to make some hiding spots and a few lava stones until i can get plants and re-scape his tank. this is also my first time doing a fish in cycle so i pulled some established filter media from my other bettas tank and used that as the base along with using bottled bacteria, his water parameters are looking 10/10. he’s eating and his rot is looking better as well as him being curious and swimming around. i can’t wait to see his full transformation