Illness/Sickness: How do I sterilize tank from Columnaris?

[Lemon3Melon]

Hi there!
We bought two juvenile axies from a pet store that was not caring for them correctly (high temp, gravel/snails present, feeding minnows, etc).
We researched a ton, and brought them home to an ideal axie home.

Unfortunately a month later we noticed one had a white infection on his mouth. We took him to an exotic vet fearing it was a Columnaris bacterial infection and found out we were right. Even more unfortunately though, the vet didn’t get the lab results till almost 5-6 days later, and did not send us home after the first visit with any medicine. By the time we got the lab results, our poor axie had passed.
She was in clean spring water in the fridge... we were upset with the vet for not starting medicine immediately. Even we thought it was Columnaris from doing our research, and we aren’t even veterinarians...

Our second axie did not show any signs of infection at that time... but then last week he was spitting up all his food... and then he got very swollen and pale. We took him into the vet again to start antibiotics.
We are giving him .01 TMS orally every day for 10 days. He’s in a hospital tank in our fridge.
We are really hoping he pulls through, but he’s so young we are nervous! The vet said he was in bad shape and gave him a 50/50 chance of survival.

My question is, if he heals in the fridge, when we put him back in the tank will he get re-infected by Columnaris in the tank water? We completely emptied the tank and cleaned it with vinegar as per vet instructions. But I read online one person said you would have to lab-sterilize EVERYTHING to get rid of Columnaris.
I read another site that said Columnaris exists in all fresh water tanks, it just infects your fish/amphibians when they are stressed or weak or ill.

Is there something I can add to our tank that will kill Columnaris Bacteria?

I can’t empty it again... it’s 46gallons and we live in a basement apartment with a half bathroom as our closest water source for the tank. Also both my partner and I travel a ton for work. These little guys were perfect pets for us as healthy pets... such little care needed for them daily. Our dog passed a few months ago and these axies are supposed to be our new lil guys... we are so so so upset that the one has passed. We are praying our second one survives and then we will buy a new friend for him.

I attached a photo of a Lemon- the golden albino who is now deceased you can see her bacterial infection.
And also a photo of a Melon- the melanoid who is currently being treated with TMS antibiotics in the fridge.

 

[Kitan]

First let me just say I have NO experience with this in axolotls and only maybe once ever more than a decade ago with tropical fish. Everything I am about to say to you is based off of research and not experience or first-hand knowledge.

Columnaris disease is extremely common in freshwater fishes and is generally considered to be ubiquitous… found everywhere. Although the causative bacterial disease agent is found in most freshwaters, its presence does not automatically lead to columnaris disease.

Also I just found the most incredible answer for what to do! Long story short HYDROGEN PEROXIDE!! Here, check it out!

https://www.caudata.org/forum/showthread.php?p=483320

"If one axolotl is displaying symptoms, that means the bacteria is present in your entire aquarium, and you should carefully check water parameters and treat any visible colonies with hydrogen peroxide before reintroducing your axies. Some excellent information on treating your aquarium with hydrogen peroxide can be found here: Columnaris and what I have learned (https://www.myaquariumclub.com/columnaris-and-what-i-have-learned-about-the-types-causes-and-treatments-1689.html)."