Betta Fish: PSA: Bacteria and Tank Water

I haven't posed here in awhile, but after my recent experience I thought it might be worth a post. Pic is most recent I have of how this little creature greets me every morning.

Let me give some background. My current fish will have been with me for 2 years this coming August. He's the most vicious little mini-shark I've ever met. His favorite passtime is to bite off fingernails and bite through the little flap of skin between your fingers and play snail-bop (you swim a snail to the surface of the water and whack it out of the water, hit the lid, swim down, catch it, and do it again. He loves to play snail bop when it is absolutely silent in the house and you need to focus with a looming deadline. "Click-sploosh-click-sploosh-click-sploosh" is the best soundtrack to help a human focus while stressed, ya know? I mention this to say he's for the most part healthy and happy.

Except.

We have been dealing with bacterial infections for more than a year, and the fin rot he's struggled with since he came home, has never really gone away. I've done it all, stressguard, kanaplex, clean water, etc. I followed all the advice before we brought him home, sponge filter, bio beads, planted tank, frozen food. And, yet, his fins would grow back only for him to get fin rot again.

Frustrating.

Then a few months ago his tank smelled like bleach. I tested for chlorine, found high levels, and moved him to my new aquaterrarium which had been running for more than 3 months. Established cycle. Levels tested excellent. The chlorine had come from the aquarium rocks and his hide that I inherited with his 10 gallon tank, I thought they were fine, they weren't.
Fast forward to a few weeks ago. I'd been dealing with cyano for quite awhile, then the fin rot came back. I would treat with blue green algae remover, treat him with kanaplex, I did everything right to keep the cycle balanced… I was frustrated because there was nowhere this bacteria could be coming from… except my tap or the air. We live in a swampy area, there's cyano in the summer in the little stream that never really dries in the back yard. It's harmless in the quantities outside the tank, but when those spores get into the 80 degree tank they bloom like crazy. So, desperate, I finally got a UV filter to add to my filter setup. I put it directly in the tank where the natural flow will circulate the water. Treated the tank one last time and set the filter to 12 hours on, 12 hours off.

It's been several weeks. Fins are growing back, the strains of algae and cyano that were a problem before are gone for good. His water smells super neutral and is very clean. He's even more of his demonic self (he bit his sitter recently). At this point I feel like he'll be around for awhile, if not because of health just out of spite. We'll have many more mornings of me saying good morning and sitting down to work, and him responding with curses on my family and ancestors (he does a big flare and posture every morning when I greet him).

TLDR: If you're struggling with bacteria and you've tried everything else. They might be in your environment. Add a UV filter to your tank and see if it helps, it may be what you need to stop bacterial spores before they root.