Questions for the pondlady: I followed all the rules, did everything you said to do, Jan, but my pond is completely green. I couldn't buy all the submerged vegetation at once, so am buying it a little every week. Oh, and my grandkids feed the fish, but only when they come over.
PL answers: Add more underwater vegetation. Without enough the pond will turn green. The fish love to eat it and, the fish will eat it faster than it grows if you don't have enough. Without extra filtration, you must have 1 bunch of submerged vegetation per square foot of surface. If not, the fish will eat it all and you will be buying it every week forever. And it's a very expensive fish food.
And how often do your grandchildren come over?? And are they feeding those fish Poptarts? If those grandkids must feed the fish, chop up some cooked carrots, or green beans. And then feed them less than a teaspoon. This assumes the feeders visit only once weekly, not daily.
Excess fertilizer will turn the pond green. Stagger your fertilization schedule if necessary. Change 25% of your water weekly until pond clears. (Don't forget the dechlor.) Changing the water is important for the pond. And the veggie beds love it.