Chilodonella can be a major threat to your koi and pond fish. Chilodonella kills fast and in great numbers. Chilodonella can survive in a wide range of temperatures. Chilodonella will attack your fish in the spring when the temperature of your pond water is low and your koi and pond fish are weak. However, chilodonella can cause great losses anytime of year, it can lie dormant just waiting for your koi or pond fish to become stressed or weak.