Gigantea have big appetite. Food bring by the clowns will not cause any problem. From personal experiences, it is hard not to feed a new carpet that start to do well in our tank.
I would not feed him more often than every 3rd day. Anemones are mostly water so a huge anemone does not have a huge biomass. Carpet tend to be able to handle larger amount of food than other species but I would not feed a 6-7 inches carpet anemone more than about 2 cc worth of food at a time.
Best to under feed him and he grow a little slower than over feed and cause him to be sick. If you read my purple Gigantea thread, I make a mistake of over feed my anemone and had a lot of heart burn for a while.
More picture would be nice. I feel as if this anemone is my anemone.