I have a new pond (installed this summer) of approximately 800 gallons. It is 12 to 18 inches deep. I have about 18 fish and some water hyacinths and water lettuce. I am not sure what I need to do to prepare it for winter. Can I keep the pump and filter going? When should I stop feeding the fish? Will the hyacinths and lettuce die with the first freeze? Any suggestions would be much appreciated.