I bought one at Macna because I was running high phosphates. It took care of the problem in no time - but like Paul said, don't run it 24/7 when you first start out. The quick change could cause problems. If I remember correctly, I started running it 3-4 hours per day, then increased an hour a day. I ran it for about 6 months - by that time my phophates were 0. I ran phosban in it. I also like the idea of running carbon in it but like Kim said, changing the media is a PIA. Much easier to empty a mesh bag over a trash can and refill. Make sure you check your phophates before you get it - make sure you actually need it. I'm not running mine now, but I keep it as backup just in case the phosphates rise again.