I'm thinking of getting a PF1 Tetrapond filter and a pump that is rated maybe 200 gph? Or should I go less? the preformed pond will only be filled up the first landing ( see here: http://www.lowes.com/lowes/lkn?action=productDetail&productId=56569-000001569-LP7918&detail=cr&lpage=none ). So like I said I only think that would be maybe 40 gallons of water. Should I go with a smaller pump/filter? Help!!