If you live in the North and your pond is just waking up then give your pond some clean fresh water. Do a partial change and clean out whatever has blown into the pond over the last 6 months. Some will argue that it will " kill the good bacteria" but all the good bacteria in the world won't help a dirty pond. Think of the pond as a very large fishbowl. If you have ever had a fishbowl and didn't change the water every now and then you know what happens. New water will give back all that has been depleted and dilute the bad stuff that has built up over the winter.