Home Products Clear Water Value Thresholds 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 Fishkeeping at the Limit From a biological point of view, many koi ponds are borderline for fishkeeping. They often reach limits that then lead to losses. Many owners suspect a lack of oxygen and aerate and pump the water through all kinds of filters, often doing exactly the opposite of what is needed.   Large fish that are sensitive to cold water, such as kois, are kept indoors over the winter if the pond has too little depth volume. This sometimes causes problems that can be traced to one of the following problems. If these explanations are too theoretical, you can find further information in the FAQs.   Often the question is discussed how to tweak the different water parameters. Normally it is hoped to get the system closer to its limit. We would recommend to set the general conditions in such a way so as to never reach these limits. In the menu on the left you'll find the most important points.