I used one of them...a few years ago on a pond I set up. Built like a tank compared to some of the other junk thats available. VERY simple to servace. The backflush works REALLY well. I still prefur a bio tower for main bio filtration but the aquadyne is definatly some quality equipment although I can only judge it on the one example...I was impressed. fairly expencive however but then it wasn't my money so.....LOL