Your fish's buoyancy issues could be caused by a number of things. Though food related GI issues are often the culprit, it could also be caused by bacterial factors, which would require the use of medicated foods. Unfortunately, some fish will remain floaters regardless of what you do for them, and for them, corrective surgery or euthanasia are two possible options. Though many floaters will continue to eat normally, if their mobility is so limited that they cannot escape the surface, they can develop lesions where they dry out. In the mean time, I'd suggest fasting the fish for a few days, continuing the pea/shrimp treatment, and seeing if you can't get some acidophilus pills from your local vitamin/health food type place. Dissolving the pill in water and soaking some pellets in it before feeding may help to re-establish the proper microfauna in your goldie's stomach. If you do manage to get him upright again, i'd suggest making sure his diet is packed with roughage, and keeping him on the warm side.