Betta suffering from fin rot or marbling??

[Navfish]

i got my koi betta recently about 3 weeks ago and he is losing some color in his top fin and I’m confused on what it is, fin rot or marbling. I think it’s fin rot because the ammonia levels have been high (1pm) the last time I checked. I’m dealing with it rn but what do you guys think? He’s in a split 5 gallon for the moment but next month, he’s going into a separate 5g. Water parameters: .5 ppm ammonia, 0 nitrate, 20-30 nitrate. Thanks!

 

[DragonScales+Doubletails]

from my perspective fin rot does not remove the color first but the actual fin. stunning betta! where did you get him? I never thought I'd like an orange betta fish but I stand corrected. it is very likely that he has the marble gene as well as the koi markings. but anyways, hope that ammonia goes down

 

[Colin_T]

Doesn't appear to have fin rot.

The easiest way to reduce ammonia, nitrite or nitrate is by doing a 75% water change and gravel cleaning the substrate every day until the levels are 0ppm.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

 

[hansgruber7]

Doesn't look like fin rot to me. Just a color change which is normal in that kind of betta. You do need to get the ammonia under control though or it will lead to fin rot and other problems. Just do large daily water changes until the ammonia gets to zero. Beautiful fish!