I used a strong dose of bleach before to try and kill something growing in my systems as well, I did it as a last ditch effort to try and save some plants. if anyone remembers that was my last pepper plants. However in the end I think I did more harm than good. Even though the plants were still living, and the
nutrient solution didn't have the bad smell anymore (but smelled like bleach). I believe the strong bleach wound up killing some of the roots. Then the dead (decaying) roots wound up feeding the pathogens even more. So in the long run, I think it just helped the pathogens by giving them plenty of food.