This product comes in 2 bottles, a powder and a liquid, totalling 850 grams. This is enough for a 50 000 litre pool for one month. It is safe, environmentally friendly, economical and very effective. A neglected pool will need a double-dose to start off, but this will effectively kill the algae and clear the water in a few days. Black algae will disappear over a few weeks, and should be brushed off the walls. (Chlorine does not kill algae, only bleaches it; this is why during a storm the choice is drawn from the water and the algae is once again visible, turning the water green.) Activator D does not hurt the eyes or skin, and swimming costumes last longer. It is non-toxic and chlorine-free, and pool run-off water should not damage plants.