A lot of people come to us and say their solution for treating their water tanks is bleach. The problem with that is if you have a significant amount of biofilm buildup in your tanks, the bleach will actually sear that outer layer of biofilm, trap the bacteria and growth inside. It'll make it impenetrable for any treatment that you put in, but the bacteria that's trapped will still be able to leach out through. So it's actually counterproductive in trying to treat your tanks.
What works much better is a product like Aquamarine Water Solutions Shock Biofilm Eliminator. It eats through and dissolves all of that biofilm layer. And when used with a disinfectant like Aquatabs Marine you fully eliminate any bacteria and be able to enjoy fresh, clean water.