Defenders 500ml Water Butt TreatmentNatural, safe, non toxic water butt cleaner treats up to 6500 L of rainwater and household water, eliminating unpleasant smells Prevents green water, soap scum, keeping stored water free from algae and slime; following treatment, water is safe for watering garden plants, flowerbeds and lawns Water butt treatment has a content indicator on the side of the bottle to assist with dosage Safe and effective water butt treatment for use outdoors in gardens;