The water has remained clean and fresh for three weeks. (Suposed to have changed it after two but it hasnt had that much use.) I do use a paddling pool cover overnight to keep out the bugs.
Used this in my kids paddling pool last month. Helped keep the water cleaner for longer. We have a 600 litre pool so I used half a sachet as the pool wasn't quite full. The kids were in it a lot! Water lasted over a week much better than before