The LFS might be referring to the output of the waterflow for the FX5. It is pretty strong. Someone with a 60 gallon was using one, and the waterflow output is splashing against the glass, therefore the "guesstimate" 100gallon. I think a 24" wide tank, and possibly a 6ft lenght, would be ideal for the FX5. I just bought two of these, and the setup consists of 7 steps. The tubing is not pre-cut. The adaptive valves are initially too tight. When I was turning it, it felt flimsy I thought I was gonna break it. This is the second day it is up and running. If I find anything else, I would post it here.