Bleach is just chlorine in a different form anyway. Sodium Hypochlorite as opposed to (I forget what the solid form is, calcium hypochlorite?). I use bleach because its cheap, readily available, effective. I just eyeball it. But i’m sure there is an optional amount. If your soil-less then it’s easy to see the roots. I go a bit stronger if they are going brown. But for easy root health you can’t beat it imo.
I use my nose a bit. If I can just smell
it, then maybe a bit much, but i’ve never done any harm to my girls. It keeps everything clean and sterile. Having said that, choose one or the other. H2O2 or Bleach. Don’t run them together. H2O2 supposedly has the added benefit of breaking down to H2O and O2 which may be beneficial to the root zone but personally I think that’s negligible. Having H2O2 on hand also helps soften up hard seed shells if you have some old seeds that stubbornly won’t germinate.
I used to use H2O2 but it’s expensive and a specialty product so if I run out it requires a special trip to the hydro store. Where as bleach I always have on hand.
Just don’t use scented bleach!