I AQUADES "31130 Algenfrei 1000ml for paddling Söll" brought together with, as we got a very large wading and I no longer wanted to replace every day the water. According to the manual, you need a cap per 200l of water, I've also done a particular way. After 3 days the water needs a little refresher. I must say I am very excited - the water is still absolutely great after 3 days, no slippery edge or something so highly recommended! I'll buy it again.