Im setting up the filtration system for my 250 gallon in door pond. My plan is to take 2 5 gallon buckets, the first one will be full of plastic strapping the the second will have some form of mechanical filtration. Does this sould good.Ive got a 550 gph pump. The ponds in my garage so it does get down to the 20's in the winter, I was thinking NC natives, what would you stock it with.