Fish are cold-blooded animals. Their metabolism is based on the temperature of the water they live in. Warmer water creates faster metabolisms, so fish will eat more. Colder water creates slower metabolisms, so they will eat less food. In fact, it’s recommended at 50 F / 30 C you stop feeding goldfish and koi altogether. The intestinal tract of the koi is about 2 or 3 times the length of their body and the digestion of nutrients can take anywhere from 2-3 days! If the water is too cold when the fish eat, the food will spoil before it passes out of their long intestinal track. This leads to all types of problems sickness, diseases, digestive problems, etc. Normally they will NOT eat when it is this cold and the uneaten food will only spoil, clog and over load your filter system. This can disturb the pond balance and possibly create an unhealthy and detrimental situation. Thus note at 50 F / 30 C and below DO NOT FEED YOUR FISH!