For that you need food especially developed for the long-term health and growth of the fish. There are many foods on the market that are designed for pond fish. Some are better than others. Our best advice is to take the time to read the ingredients listed on the label of the food. Avoid the ones that have ground corn listed as any one of the first 4 ingredients.
Many grains are a cheap source of protein and tend to be hard for ornamental fish to digest.
Most of this protein goes through their system without being digested and out as waste, taxing your filtration system. This adds more ammonia to the water. If you are having problems with ammonia build-up in the water, check your food for a high content of grains. A good food for your pond fish should list fish or other seafood meal as the first ingredient unless it is a wheatgerm food. If wheatgerm or wheat flour is listed first it should be followed by fish meal.