It is essential that you perform regular pond tests during the early stages of your pond and when you add new life to it. This is to ensure that the various chemical levels are acceptable. Once your pond has been established and you are no longer adding new life to it then you do not need to test your pond as much. Below are my pond test results performed since the pond was created, as you can see I did not strictly follow the rule of adding fish gradually. I did intend too but after adding the first three I was given the opportunity to get 9 reasonably sized gold fish and shubumpkins for free from a friend. As you can see after adding the 9 additional fish the Nitrite level came close to being dangerous but it soon recovered on its own (without any additives) and is now back down to an ideal level.