so are were putting on "blinders" to say buy "wild caught"??? it sounds like a gamble us fish people have to take in the hobby, the risks should be lower from wild caught, rather than coming from poorly farmed fish, but we have polluted the world, even remote areas... I think
@GaryE ... described wild catching fish among the garbage, in the wilds of Africa... plus we have to assume these bacteria are in nature as well... but in the grand scheme of water changes, you can't get better than nature, as far as shear volumes of water changes...
Fish TB has to be introduced into some areas for it to become established. Having rubbish and chemicals in the environment doesn't introduce TB but when governments release tilapia into Lake Wanam and other places in countries like New Guinea, then those tilapia can introduce TB to the area.
As a general rule, wild caught fish should be less likely to carry Fish TB but if they are put in a shop tank or a holding facility that has TB in, there's a chance they can get it.
I did ( & do we ever really get rid of it ) had Mycobacteria in the tank that I had the rainbows in... so is Mycobacteria on your gravel, a guarantee, you are getting fish TB... are they directly related??? do sick fish introduce it to our aquariums??? how did it get here??? it's certainly in nature... big patches of it can be witnessed in many places...
The Mycobacteria gets shed from the fish and ends up in filters, on plants, gravel and ornaments in the tank. There's no guarantee other fish will pick it up from the tank, but there's a pretty good chance they will just due to the numbers of Mycobacteria cells that end up in the aquarium.
It gets introduced into aquariums via infected fish and or contaminated plants, ornaments, gravel, etc, or water from an infected tank. Unfortunately you can't tell if a fish has it until the fish shows symptoms. So even if the fish looks good when you buy it, it could have a few Mycobacterium cells growing in it and the fish won't show symptoms for months or even years after you get the fish.
I've never been a water change fanatic ( like some members here ) but maybe we ( the hobby ) did this to ourselves... when I had tanks long ago, water changes were just done, when doing major tank cleanings... I was an early proponent of growing terrestrial plants out of my tanks, even 20 years ago, and with the advantages those plants provided... I mostly just refilled evaporation ( which is not a water change BTW... )
so what do we really do now... it sounds to me. like the water change fanatics, had it right all along... if we can reduce the bacteria numbers in our micro environments, it may reduce those numbers our fish are exposed to... so our drinking water is bacteria free... right???
Clean tanks don't necessarily help prevent Fish TB. I religiously did my tanks once a week and I did big water changes, gravel cleaned the entire substrate and kept things spotless but my fish still got it. The water changes and gravel cleans might have helped a bit but they didn't stop fish dying from it. It's just luck of the draw, either the fish have it or they don't.
Drinking water is not necessarily free from it. Mycobacteria can tolerate low levels of chlorine for a short time (hours or maybe days), and tolerates higher levels of chlorine for less time (a few minutes to hours). Theoretically any bacteria in our drinking water should be killed by the low levels of chlorine or chloramine in the tap water, but there is not a 100% guarantee. However, even if there is a few Mycobacterium cells in the tap water that survive, they are unlikely to survive our stomach acids.
Mycobacterium cells have a waxy coating around them and this protects them from chemicals, drying out, and immune systems. If you can get rid of the waxy coating, you can kill the bacteria quite easily, but the hard part is getting rid of the waxy coating. Chlorine (household bleach or swimming pool chlorine) mixed with water and left in contact with infected items will break down and remove the waxy coating and usually kill the Mycobacterium cells. The items can then be rinsed under tap water and sprayed with 60%+ alcohol to make sure the TB cells are dead. Vinegar could also work after bleaching.
Heat also kills Mycobacteria and 60C for a couple of minutes will cook it and kill it. Sunlight does not kill Mycobacteria unless you live in a desert or have really hot days (40C+ in the shade) and the Mycobacteria is in the sun where it heats up to 50C for an hour or more.