We usually start the pump up when the weather is warm enough for us to be out and about in the garden, usually around April. I put filter mats in to trap the debris, add Aqua-One, koi clay, and activated charcoal. Pond water is normally clear even before starting up the pump. This year I have tea colored water because my net broke in the middle of winter and lots of leaves fell into the pond. But water is still clear. Between the filter mats and activated charcoal, my pond will be back to normal in a week or 2. I don't vacuum the pond until about a month or so later, usually in mid to late May. After vacuuming the pond, I always add Chloam-X in before adding fresh water back into the pond since I've city water.
HTH.
Kuan