i use just regular peroxide with the best results all the way till the end.. no issues.. when i clean i use bleach water. and add a table spoon of it with every fill..no root rot. white roots and even taste like bean sprouts..
i dont but a friend of mine would add a small amount of bleach in his rez when temps got up and never had a problem after that. i know he had used hydrogen peroxide before using bleach and didn't have as good of results.