I have been running a FX5 for about 2 months now I decide to clean it. I wanted to check it out to see how bad it was in my CA/SA, Needless to say it wasn't that dirty for fully stock 125gal. Note this is the only pump runing on My CA/SA and works like a champ. So I bought a 2ND FX5 last week and was going to install it on my 125gal african which is really stock. So this tank has been running a Eheim Pro 2 and a Eheim Pro 3 and it never stays crystal clean or clear and I have to admit that it's overstock with a good group of Fish mainly (12) Frontosa yes I know they will be getting there own tank (300gal) don't worry. So I took out the Eheim Pro 2 and install the FX5 and with in two days the tank is crystal clear and looks awesome, all in all I'm amazed with how well and How awesome this pump works. If I would have known about this pump I might have bought it instead of my Eheims but I did run my pro 3 Eheim on My CA/SA for 1yr and half and never had a problem but when I overstock it I over worked it so that is why I need the extra pump.