I assume it's possible. They can't really become resistant to high concentrations of cleaning products like chlorine bleach because they just physically ruin t

I assume it's possible. They can't really become resistant to high concentrations of cleaning products like chlorine bleach because they just physically ruin the organism - the best explanation I've heard is that that would be "like a human becoming resistant to lava." Not gonna happen. But in really low concentrations like in a pool, perhaps they could resist the oxidation effects...