Although all of the koi pond supplies, which makes up the entire koi pond system in your home, are a crucial element in keeping your koi fish alive, it is the pond filter which allows live bacterias grow, multiple and break down the koi fish waste from building up. As a koi keeper, take some time to learn about the nitrification process and how you can prevent your fish or koi fish from being ill. It will save you a lot of money and many dead fishes.