Do not obtain the freshwater mussels until the water shows a tendency to greenness ; there will be no food for them and so they will die. When necessary half a dozen will be sufficient.

The small crustaceans may be collected from a slow-moving stream or pond in the country, care being taken that no undesirables are introduced into the pond with them. The pond is now stocked and all that remains is for it to mature ; this it will do in its own good time. The water, in the ordinary course of events, will not require changing. After a few years, dust falling on the surface and sinking to the bottom, detritus from plants and so forth, will cause silt to form on the bottom. If this becomes objectionable, or if the fishes seem distressed for no apparent reason, the pond may be emptied and cleaned out. Ordinarily, however, the pond should stay ' put' for years.

If ice forms on the water it should be broken to admit air ; the fishes will be sheltering in the deepest part, but if the ice is not broken they may suffocate. The less hardy species should be netted and kept in tubs in a greenhouse or in indoor aquariums at the approach of winter. Fishes are sometimes caught unawares by a sudden frost and may get frozen up in the ice ; in this case the fish, and part of the surrounding ice, should be placed in a bucket of water of about sixty degrees Fahrenheit and allowed to thaw slowly ; if the fish is thawed out quickly the sudden change of temperature may be fatal.