Hi David,

I don't know if bleach is the cheapest way. The chlorine percentage in bleach is about 10-15%. In swimmingpool tablets it's 60-90% (depending on the brand/type). Whatever you use 2,5 mg/liter is the recommanded active chlorine level for swimming pools and should be sufficient for desinfection. For both methods you also should check the PH-level. If the PH-level is to high or low the chlorine won't be effective.

Mark