Im currently running 2 fluval fx5's and a emperor 400 on my 120g. I have another fx5 on order and an emperor 400 in the box. I will be using the 2 fx5 on a future project!!!
i have atleast 2 filters on each of my tanks. I clean one one week and then the other the next. I learned with my magnum 350's ( I know they aren't HOB's) that regular cleaning keeps them perfoming like new.
110 on a 40 should be great. The flow would give water a good bit of oxygen and clean the tank nicely unles you seriously over feed or also have a messy pleco.
my 110 was kind of noise today, rinsed and now quiet once again... gues in a few weeks ill check my canister.