Ponds are just like aquariums... they require time to cycle. Basically what you're waiting for is the good bacteria to become well enough established that it is able to eat the waste from your fish. There is also a certain point where the nitrite/nitrate/ammonia all balance each other out.
You may be able to do daily water changes to help offset the fish waste, but this will make it take longer to cycle, and just must be careful during this period to not allow ANY chlorinated water into the biological portion of your filter.
There are also bottles of biological bacteria available for sale, this should help speed up the process of reaching a balanced point. Most brands only contain one type of bacteria, but I believe there are three beneficial types (and of course they won't say which particular type they contain). If you can find a brand that states it contains more than one type of bacteria, it will help the quickest.
By the way, can you give us some details about your pond size, filter setup, and what sort of biological filtration you have?
