Algea can't grow in the dark - period. It's a plant after all. If you check out Peggy Hall (head and water fame) she promotes a lower concentration of chlorine for the 24 hour shock treatment. It really does not require much at all to kill any and all critters. Over chlorinating has no extra benefit other than eating at your plumbing
. You plastic hose really would prefer a lower dose. One cup household bleach per 100 gallons is enough.
Mineral deposits could be common in tanks after a prolonged use from hard water and the chlorine won't really reduce it to any significant extent.
CLR is poison.
You can rig up a household two stage filter that you connect to the water supply line with some washing
machine hoses so you filter the water before you put it in the tank. That is a more proactive approach to keeping the tank cleaner and promoting better tasting water. What never gets in won't ever give you trouble.