I have this filter, the 4000 one. Not too impressed - have to dismantle it twice a wwk and clean the sponges. Backwash is kinda useless imho. I also have a pondmaster PUV 4000. Much easier to clean but has no sponges. If my water ever clears, the pond master only requires cleaning every 3 or 4 weeks.A few years ago I had a cyprio pressurized filter -never had water problem. Gave it to my dil and her water NEVER is green or cloudy,