Fin Rot- Trying to diagnose and treat lone betta in planted tank.

[LegalEagle2009]

What about that white fuzz I see on the heater (in the latest pic I showed)?

[callistra]

I don't know that that is. Maybe a bacterial bloom or slime mold.

[sarahspins]

Originally Posted by LegalEagle2009

Two changes yesterday put it back in safe range. One 50% change today put it back in safe range again. Will check it again tomorrow.

I would expect that it needs changing again tomorrow. Without a filter (even with plants) you WILL continue to keep seeing ammonia. That is normal, because there's nothing in the tank to convert it to less harmful stuff. You are currently trying to treat the effects of your betta being subjected to ammonia you will need to continue to daily water changes - personally I'd continue do them while your fish recovers even if your ammonia levels look like they are 0.

It's almost impossible for your ammonia to go from .5ppm to 0 with a 50% WC.

Are you testing with strips or with a liquid test kit? The strips are often referred to as "guess strips" for a reason.. they're notoriously difficult to read and often known for being inaccurate.

[LegalEagle2009]

It wasn't a single 50% water change. I had done two 50% changes last night. This was the third 50% change.

Yes, I used a strip. I haven't found them difficult to read.