For tanks that always have water, I found light chlorine levels work and have been using it since the 70s. I use a pool test kit and go for barely showing on the lowest level.
As water is used in the tanks, vents allow air carried bacteria to enter the tank at every reduced volume change. W/o some biocide in the tank, it will always harbor some growth, including the lines, too. I solve the chlorine problem by having filters at the galley that absorbs the chlorine and other taste issues for all drinking, cooking and ice cube water.
Before writing this, I talked with a friend that owns a 30 year old commercial aluminum boat. He uses a similar method for growth control in his tanks. His tanks have ports and are big enough to stand and walk around in. Probably thicker aluminum than yacht tank material. He finds only light shallow corrosion.