Hi all! So happy to have found a place to ask questions since I can't go to the store right now! I think I have decided on the PONDMASTER 02722 1200 GPH Magnetic-Drive Utility Pump based on a recommendation from neighbors (who's pond is the inspiration for this build) but would love a filter recommendation. The pond will be between 500 and 700 gallons, will house goldfish and have a waterfall. This is all a little overwhelming so thank you!