To obtain maximum production, yes. Fertilizing a pond may increase production by 30-40% over non-fertilized ponds, but feeding the fish an artificial diet will further increase production by another 30-40% or more.

However, if feed is very expensive or unobtainable, then it may be more economical to just fertilize the pond only, and make do with a lower production, but at lower input costs. Each situation is different.