I just got my FX5 and it sure is nice. It really pumps the water through there. I'm also suprised how much biomax I was able to load up in trays. I was thinking about getting 2 for my 125 gallon, but after seeing it work I think that it would be serious overkill. I'm thinking that one of these bad boys could probably filter a 200 gallon tank, especially with an AC110 hanging on the back. I was also very happy with how easy it is to work on.