You're thinking right about the lift tubes, but HMF's can be used on any size tank. Do you have the fancy Jetlifters/airstone and PVC/something else?
Best flow rate depends on foam dimensions and porosity. Turnover rate for fine foam shouldn't be much more than 1 to 2.5 times per hour and coarse no more than 4 to 5. Post the foam dimensions, and I can run them through a flow calculator if you'd like.