i got a 2000 gallon pond at home. I use a net that you can buy at any pond place ( protects from raccons and harons. For the water quality i would recomend buying water clearing bacteria (it works great). Just so you know koi produce 5 times more waste than goldfish. Do not feed them for 2 more weeks ( they are hibernating so if you feed them they will die). Start off with 6 goldfish and 3 koi. The koi will get 1foot in 2 years. ( i got all my koi 4 years ago never lost one and now they are 3 feet long
). Get alot of plant cover for the pond and hiding spots. How deep is your pond? Don buy big fish now. What is your ph?