Home Products Clear Water Value Thresholds Temperature Galleries Service Forum Contact Search Masthead Home Naturagart Products Plants The Park Visit Diving Park Magazine Shop Ponds Clear Water Filtering Trench Target Suction Technology Filters Pumps Pump Wells Pipes Skimmers UV-Filters Assembly, Regulation Information About Streams Basic Knowledge Value Thresholds Temperature Nitrogen pH Oxygen Carbon Dioxide Water FAQs Water Features Garden Electrics Green Roofs Pavilions Greenhouses Nesting Aids Threshold Values: Temperature High Temperature leads to high intake of food and consequently to high levels of excretions. These excrements have a strong influence on the quality of water. In high temperatures a deficit of oxygen is also more likely. If  the pond is not completely under control, feeding should be strongly reduced. Low Temperature The life cycle of many species includes a winter break. Grant your fish a winter holiday. Many species actually need this if they are to be able to reproduce the following year. Hence, the winter break isn't a torture for your fish, it keeps them healthy. There have been cases where fish have stopped feeding completely for a whole year. The less you feed, the better they will get over the winter.         Drop in Temperature The high or low temperatures are often not as critical as the speed with which they change. Below certain temperatures fish will stop feeding. If the transition is slow like in nature, the intestine is completely emptied. If the temperature drops too quickly, the fish will stop digesting, the contents of its intestine rot and can kill the fish. Often people have a wrong idea about the time fish need to adapt: If fish are kept at above 10ºC and are then changed to 2-4ºC their breathing is paralysed. A safe adaptation takes 3-8 weeks. A drop in temperature from 20ºC to 10ºC is also frequently fatal. This often happens in spring when the fish come out of warm wintering and are put back into the pond that is still cold. Rise in Temperature Make sure that the temperature doesn't rise too quickly after the winter break. If, for example for Cyprinids, water temperature rises from 4ºC to 20ºC in 4 hours, the fish is so stressed that it mobilises up to 50% of its fat reserves in the following 14 days. If the reserves are insufficient to cope with this stress, it will probably die. Temperature and Feeding Many fish are bred in the cooling water basins of power stations. The warm water leads to intensive ingestion of food which normally doesn't agree with them. Free range fish grow at 20-50% the rate that  farmed fish - or pond fish - often do. Note: Fattening will often make fish ill. Less food makes fish stabler and more vital.