We had a waterfall put in last year and the gut sold me on the Aquascape system. He said I would have to change bags every six months. I had long strands of algae after 4 months and checked to find that the Aquascape Prevent bag was empty. I replaced it and ordered the Aquascape Clean and have used four of them. We had a lot of water leaking and had to keep refilling the basin. So we may have been losing the effectiveness of the Aquascape products with the water loss. I've used eight bags and this is the 12th month, not quite a year yet. I think I need to replace the bad again soon. I'm using the Clean because it's less expensive than the Prevent.