Hello, I have a small pond for my ducks, approximately 60-70 gallons, and would like to set up a DIY gravel filter system. Can anyone recommend a good pump? I want something that will be durable, and relatively energy efficient. I will probably set it up on a timer to run a certain number of hours each day, but depending on how much it has to run to keep the water clean, I don't want to kill my electric bill... Any tips will be appreciated! Thanks.