It all starts with water quality. Give it a little time and check alkilinity. If it is OK and a sechi test is good, I wouldn't fertilize. Fertilizer has a place just like any other tool or medication. However, an over dependence on something you really don't need doesn't make sense and, like medication, can be harmful. I have posted before that I have stopped fertilizing due to DO crashes. However, it can do a beautiful job of jump starting a new pond. An alkilinity test might say that you need to lime before fertilizer will work. It takes time before alkilinity leaks from the soil so don't get in a hurry and assume you need to lime. Check with locals about their alkilinity levels or ask if you can test it if they don't bother. Back to fertilization: Bob Lusk once posted that you shouldn't fertilize if you don't need to. Bill Cody once posted that if you start fertilizing, don't stop, I respect both of these guys opinion.