My pond is roughly 500 gallons, a friend of a friend is having to empty theirs due to ever increasing grandchildren, his filter is quite a good one and is for approx 5000 gallons, would this make a huge difference as to what size filter I have or will it just keep it extra crystal clear. Please dont laugh at my question as I am relively new to pond issues and as I havnt been offered it for sale yet I dont want to ask, but if its suitable I will mention this to my friend.