Unfortunately we live in an are when information is easy to pass along whether it is correct or totally wrong. We see lots of folks who read garbage and assume it is correct and chlorine, tap water and bleach ae part of this folly.
This info seems to sort out in this way?
1. Tank water is good for fish as it has the chlorine removed if it has been added. Good stuff!
2. Tap water is good to drink but will kill fish if we don't remove the chlorine. Good stuff but we have to be careful.
3. Bleach? Terrible, scary CHEMICAL----run away!!!
As I see it, a better story is that they are all pretty much the same other than the amount the chlorine is diluted. Sounds insane to speak of bleach and tank water as the same but let me explain why I say this.
Bleach is sold in bottles for all kinds of uses like laundry and often labeled as 6%. When we store it on a shelf, we need to keep the chlorine content reasonably steady so they tie it to a form of salt and we keep the jug closed so the chlorine doesn't leak out. Tap water is far more diluted so that we may add a teaspoon of bleach to 50 or 100 gallons so that we maintain something like 3-10 PPM but since it is not tied to the salt, the chlorine begins to escape as soon as we pour a glass of water. Sensitive people can often smell it as it gasses off and leaves. In our tank water we want the chlorine content to be too low to measure so we add something like Prime, Safe or a dozen other products to change the chemical structure. We could do the same thing by adding a few thousand gallons of water to dilute the chlorine content to such a low level that we could not measure it. But that gets really awkward, right?
One could just wait and let the chlorine gas off IF one is sure that it is only chlorine and not chloramine. With chloramine, the chlorine is tied to other things to keep it in the water longer. It used to be standard practice to just let water set to remove the chlorine but now chloramine is used in larger supplies and many of us do have chloramine in the tap water.
Like most things we do, it pays to learn what we are dealing with and treat it as needed.
I find it a whole lot easier to figure out how much chlorine I want than it is to figure out how much of that terrible, scary potassium nitrate to use!!!