my 150g had 2 fx5's on it was working well but both were setup for bio mostly... and wasn't getting the crystal clear water like I use to, so I opted for another filter and well I ended up getting a wicked deal on a used fx5 so I packed it full of sponge hahaa, one layer 3 filter floss pads, another layer 2 filter floss and one fine filter, and last layer with carbon to help reduce any smell .... so after a couple days we will see what 3 fx5s can do for a 150g tank hahahah 