The protein skimmer you have is designed for salt water and wont provide the proper amount of bubble production. Freshwater foam fractionators are at least twice the size and produce twice the flow. There are many freshwater aquarium people using skimmers, but usually the skimmers they use are modified marine skimmers or DIY skimmers using marine parts like the needle wheel pumps and high volume venturis.
I have had some success with foam production right after a feeding, but the foam production falls off not long after. Increasing the aeration will produce a consistent foam, but I haven't seen a benefit yet and it takes ALOT of aeration. Freshwater just doesn't have the density saltwater does and therefore, the bubbles don't last long.
I will say this; if you are able to produce superfine bubbles and very turbulent water movement, you will produce foam(skimmate) and it will be cruddy and nasty just like a marine setup. It takes a little ingenuity and some tweaking, but protein and other junk can be removed with a skimmer in freshwater.