A grating can be placed just under the surface of the water to prevent a child from falling in or a dog from jumping in. Top off the pond if it becomes low. Remove filamentous algae. If algae are a problem, reduce feeding and increase shading. Use algacides only as a last resort.
More fish die from poison gas accumulation under the ice than from cold temperatures.
Use a heater to maintain a hole in the ice. Do not open a hole with a sledgehammer or damage will occur to the liner and the eardrums of the fish. Once a year, preferably in September, clean organic matter from the bottom of the pond, cut and remove excessive root growth, and trim water lilies. Cover the pond with netting to catch fallen and blowing leaves during autumn. Ponds provide endless enjoyment for their owners, from the fish which anxiously await feeding time, to the colorful blooms of the lilies, to the sounds of falling water and croaking frogs at night.