Actually, it's the hoses that get bad the most. Not sure why people think it's only the tanks. If the tank is dark you can't grow algae. It's one of those because it's bigger things. It's the things that grow that you are out to get rid of. Anything green requires sunlight, and it does not need all that much. The hoses usually get a little bit of light in several places even if it is not so obvious.
The drug store H2O2 is 3%. Household bleach it also pretty tame too. Both can do the job handily
even at diluted concentrations. Bleach at 100:1 is enough. You really don't want to mess with strong stuff. You are gently cleaning
the water system you drink from not eradicating toxic waste. Concentrated H2O2 or chlorine will trash the plumbing
and do a nasty job on your skin.
At best you are attempting to kill off some pretty much not so bad algae and maybe some other critters you captured and held hostage in the water system. If your water system is worse than that then you should be in the hospital. Water born parasites will die from the same treatments, but if you have them inside you you need medical
treatment and treating the water system won't cure you even if it should be done. If you are not sick then a very mild treatment on a couple times per year basis is a measured response.