David
What size model of the Ultima do you have? How many hp is your pump? Do you have a skimmer and a bottom drain? Does the water from the bottom drain go to a settlement chamber of some kind by means of gravity flow then to the pump and then Ultima or do you simply pump the water from the pond directly to the Ultima? Also, you mentioned media that polishes the water, what do you mean? What kind of media? During this time of year, I would backwash that Ultima at least 2-3 times a week or more if possible. It shouldn't take that long and your water quality will greatly improve.
The foam you have on top of your water is most like caused by DOCs (dissolved organic compounds) and they need to be addressed with proper water changes. Also, it sounds like you're feeding too much. Back down to once a day in the morning until you get the DOCs under control.
Mike